Well, not exactly. When you reach level 58, you can visit the NPC outside of the Outland portal that is in the Blasted Lands. He gives you a quest to enter the portal and speak with an NPC on the other side, who sends you to the flight master, who sends you to Thrallmar to speak with yet another NPC. That NPC sends you to another NPC and then you can begin questing in earnest.
Anyway, the NPC that you speak to after you land at Thrallmar? His quest (smack dab in the middle of a chain of quests) is obtainable at 57. When the group was in the 40s, I used my level 74 mage to port them to Shattrath and my level 74 warlock to summon in the one character who shared the mage's account. So they were bound in Shattrath and I had decided to get the flight paths and some discovery experience while I was still 57. Upon reaching Thrallmar, I was surprised to see the yellow exclamation point over the NPC's head.
Long story short, you can complete that quest (for something like 4,250 exp) but when he attempts to give you the last quest in the chain, you get a message to the effect that you're not of the appropriate level. The rest of the quests in the chain can only be accepted at 58, except that when the flight master attempts to give you the quest you completed at 57, you get a message reminding you that you already completed it. Then when you arrive at Thrallmar, you simply skip that NPC and complete the quest chain.
The reason I was running around Outland at 57 was that questing in the old world had just about dried up*, and I still had most of that level to go. I had skipped the Carrion Grubbage quest in Eastern Plaguelands because I remembered that the drop rate wasn't very good. With few options, I decided to do it, and it turns out that the drop rate has been significantly improved. It was above 75% and possibly higher, and I didn't have problems finding grubs to kill. Maybe they increased the spawn rate or the number of grubs, or maybe I'm remembering it wrong, but the quest didn't take as long as I had feared. After that, I went to Winterspring and took the quest to kill Ursius (which I had abandoned previously, since I couldn't find him at the time). I completed that one and finished the chain by killing Sky-Rotam. On the way back to complete the quest, I saw that I was about 16,000 experience short, and remembered that I was getting more than 8,000 experience for desecrating the Alliance bonfires as part of the festival event. So I figured I'd do that twice more and finally get level 58. But to my pleasant surprise, the quest completion for the chain that started with Urius is just over 16,000 experience (one turn in for 11,900, then the NPC gives you a second quest to speak to him again, which granted something like 4,750).
*Bear in mind that during the level grind, I was skipping quests that required lots of grinding for quest drops. In the lower levels I did those quests with very rare exceptions, but over time I skipped them more frequently. Kill quests are perfect for a group, but collection quests can become a real grind, even though the ability to bind the "interact with object" function to a keypress has made collection quests much more tolerable.
So I was finally 58 and headed to Outland to start gearing up. I had geared the team up almost exclusively from quest drops, and that leaves you fairly lacking at level 58. The first few quests in Hellfire Peninsula provide a weapon upgrade, as well as armor upgrades for the head, chest, and leg slots. These provided a very nice boost to the team. One funny aside-- after completing that quest and upgrading the hunter's bows, I was dismayed to see how often they were missing with their shots. It couldn't be the level difference, I thought-- I'd killed mobs that were 10+ levels above me in the past. And then I happened to notice the text window on one of the hunter's screens:
Your skill in Crossbows has increased to 125
Your skill in Crossbows has increased to 126
Your skill in Crossbows has increased to 127
Your skill in Crossbows has increased to 128
Your skill in Crossbows has increased to 129
The icon for the hunter upgrade was that of a typical bow, not a crossbow. But the weapon is indeed a crossbow, and although my hunters had trained the skill, they'd never used one before. So the excessive missed shots were due to the fact that they were starting from a skill of 1. But with four of them firing away and the pets keeping the mobs busy, it was not a problem aside from taking a bit longer for stuff to die. Once their skill got into the 240s, they rarely missed anymore, and things started to move quickly again.
Anyway, once I was in Outland, the experience came much quicker, and they hit level 60 in short order. Along the way, they completed the quest to kill Blacktalon the Savage, a level 63 elite that is not a pushover for a modestly-geared team of level 58. I also completed the quest to kill Arazzius the Cruel, another 62/63 elite that is a bit tougher than Blacktalon. I completed the latter quest first, losing two pets only because I had moved my pet heal button and the pets weren't getting the periodic heals from the hunters while my shaman spammed heals on herself to deal with the spawned adds (which despawn after a certain amount of time, to my relief). The group also killed an elite 61 orc that roams around the edgeds of the road to the ramparts.
Having gotten to 60, they then completed the long series of quests that lead the player to encounter the Maghar faction. It's a ridiculously easy quest line, requiring only some running back and forth and simple interaction with quest NPCs. You do not have to kill anything to complete the quests. There are five or six steps, and each one rewards just over 10,000 experience, with the final quest also providing a piece of gear. You can then get a short series of similarly easy quests from an NPC in the Maghar grounds, which provided a new bow for the hunters and a new staff for the shaman. It's a lot of exp, a lot of gold, and two pieces of gear that you earn for mostly just running around.
Having ground out levels 50-60 with a lot of play time, I will start to scale back my time spent and work through Outland at a more leisurely pace. But I figure I'll be at level 68 and ready for Northrend before long, since the experience curve from 60-70 has been lowered by a fair amount and the experience granted from quest turn-ins has been boosted significantly. The upcoming patch (3.2) will lower the costs to increase your riding skill, as well as boosting the flying speed of the slower flying mount (from a 60% increase to a 150% increase!!!). So for now I'm still on my slow ground mounts. The patch may not arrive for some time, but that shouldn't be a problem. At 68 I will almost certainly head to Northrend, which means that flying won't be an issue until level 77, and by then the patch should be in place. Otherwise, by then the group should have enough money to upgrade to fast ground mounts and slow flying mounts from drops and quest rewards anyway...