As someone who has followed the game in the United States for a long time, I would like to clarify some things:
Bob Bradley has been in coaching since 1981 when he was head coach of Ohio University. He was Arena's assistant at UVA and head coach at Princeton before becoming Arena's assistant at DC United. Needless to say, he had plenty of experience that qualified him to take a coaching job that a LlaMa might not realistically have.
Bruce Arena was a pro player and was one of the best coaches in the college game before he took over the US U23 team and then DC United.
Fernando Clavijo, Preki, and Frank Yallop all had built a reputation as a player, much like Gareth Southgate at Middlesborough and Roy Keane at Sunderland, who are there at their first coaching appointments. Clavijo, Preki, and Yallop also all had assistant coaching positions before they became head coaches. Needless to say, you definitely need a reputation within and at least a little experience to coach in the MLS.
I have lurked alot on this forum (I'm actually working on my first update right now), but after reading the rules a few times, it would seem that technically it is OK to manage in the MLS (and might be a good intro for those who are new to the LLM way), but should probably be avoided by experienced players because it is not that much of a challenge. There is little disparity in terms of resources available to the teams, and there is fairly little difference in squad quality at the beginning of the game. Also, the playoff system allows one to finish as low as fourth in a conference of six and still win the title. It is fairly easy to win continental competition as well.
For those of you wondering about the draft, it is not as complicated as it seems, I'll attempt to explain it: Every off-season a pool of players comes together in the MLS Combine to form four teams. These players are randomly selected in the game I believe (in real life they choose themselves whether to be available), but they are a combination of young players from colleges and the lower divisions of the US leagues as well as out of contract players, mostly Americans with the occasional foreigner thrown in. Each team plays each other once. The competition is of no consequence other than to demonstrate the skill of the players. After that, each team gets to pick a player each round (there are four). The team with the worst season record from the previous season picks first while the champion picks last, and all the other teams fall into place accordingly. There is also a Supplemental Draft, which I am not entirely clear on, but it works in much the same way as the Super Draft, it is just different players that get drafted.
In the game, draft allocations are used to negotiate transfers. Say you are want a player, and you offer a team who owns the player your pick in the First Round of next year's SuperDraft. If the transfer is accepted and goes through, the team who receives the draft pick gets to pick a player in the First Round (or whatever round you offer) instead of you (essentially they get two picks and you get none), and you get the player. Keep in mind that the draft is where most of the top young talent emerges, as most players in the United States play in college before going to a fully pro team. In a sense, the colleges here are like the youth academys in England except that they are not affiliated with a certain club.
Hope this helps explaining the MLS (if not I can give it another go), and I'll be back soon with my update (I'm giving Fisher Athletic a go).