Having David Beckham play for the LA Galaxy is not going to help in the long run. The man is more popular/well-known than Shaquille O'Neil, Peyton Manning, and A-Rod combined. His jersey sales account for a large percentage Real Madrid's (his former club) merchandising. And there will be a bump (like when Pele playing in New York) in interest while he is here, but after he leaves, it will go back to moderate interest.
I've been a pretty steady MLS watcher since their inaugural season. Go Revs! One of the best moves that MLS made to get ready for this year is to partner with the German footbal league who will teach the MLS guys how to position the camera, how to light the fiely properly, how to shoot from multiple angles, to better portray the game on television. We might even get to see a couple of good exhibition matches between the good German clubs and the US teams. I think having a high profile player like David Beckham on someone's roster will be a good start and might attract some better international players to the game here in the states. The first couple of years we drew mostly from South and Central America and out play was very much like what you'd see from the Argentine, Mexican, or Venezualan clubs (all of which you can see on Spanish Language Cable). But as more Europeans are drawn to MLS that will change. I don't know if it will draw more fans, but it will certainly make for better and more varied football play.
I have to throw in my two cents on this, because I have actually given my explaination on this to several of my German friends.
The MLS is priced like a professional sport, but it doesn't have the following. We follow as adults the sports we followed as kids. As kids we followed the sports our families followed. To break this cycle the MLS has to get as many butts as possible into the seats at the games. Once people see games live, they become interested in the team in general. As interest increases, demand for soccer on TV will increase. Once the games are on TV, more of the soccer league kids can see the games. This creates more interest in it just spirals up.
To get more butts in the seats the MLS needs to almost give the tickets away. Special deals to teams or families with kids on teams. Lower the ticket prices in general.
15 years ago I never heard of people crowding a minor league baseball game. They were played out in the middle of nowhere and no one went. Then in the Philadelphia area they moved in two teams, One in Trenton and one in Camden. These teams did well, because it was an affordable option to going to see the pros.
A soccer game needs to be cheaper to see than going to the zoo or maybe even a movie. Make it the place a father takes the kids on saturday afternoon, when mom wants a day off.
There are tons of kids playing soccer who want to follow a pro team. They just need to see the team.