Since I'm at Fort Irwin now, I'll pop in my two cents.
Live on post if you can, but the housing isn't completed yet, so you could end up a sh*thole. If you don't mind the drive and don't have a gas guzzler, I recommend living offpost. That's just me, though, but I think the benefits outweigh the crappy parts of living off post. Yes, living off post makes for a long day. I leave at 0530 and get home a little before 1800. But from here, I'm only 30 minutes from the nearest mall, so I can pop on down there for dinner and its' not a big deal. To do that from post is more than an hour's drive, not something most people will do on a Friday night. Or I can take a day trip to LA or Ontario and I'm not really put out.
I've heard some people make the argument that you are so far away from the commissary and medical facilities, but there is a Marine Base right here in Barstow with all that. Also, the drive is a killer, but usually there are people in your unit you can carpool with. I spend $60 a week on gas (I drive a 4 cylinder, manual trans Saturn that gets 30 to the gallon) and on the weeks I don't drive, I get to sleep the whole way in. Plus, the 35 minute drive home is a great time to decompress from the day so by the time I get home I'm in a great mood.
Apartments off post are just like anywhere else. Some are nice, some suck. I've lived in two complexes in Barstow, both were really nice. Stuff to do: Barstow does have a movie theater. It's an older one, but it's decent if you don't feel like driving to Ontario or Victorville. There is also a drive in that plays movies on Friday and Saturday nights. And beign SoCal, it's open year round. I believe it's $6 per person for a double feature and they do play new movies (I saw Pirates of the Carribean 2 opening weekend followed by Cars for instance). And you can bring the dog there. If you guys like to go out, there are a couple decent bars and a bunch of dive bars. I recommend Vick's. They are very military friendly and just a really nice place. And I don't just say that because I'm friends with the peeps who own it.
And of course, Vegas and LA are two hours away.
Stuff to do on post? Reggies, bowling, movie theater and Outer Limits. I don't recommend the OL. It's kinda club like on the weekends with a male to female ratio of about 4to1. I've been there once and felt very uncomfortable there and haven't been back.
Deployments. They happen here just like everywhere. I believe 11th ACR is scheduled to go again in 2008. That's the rumor. There is also an EOD unit that deploys as well as various support and maintenance units that deploy. This is very much a deploying post, though not as much as places like Hood or Bragg.
I know this is a bit lengthy, but I hope it helps. If you PM me your address, I can send you a welcome guide. It's pretty thorough, and I don't just say that because I put it together. Any other questions, let me know. I've been here over two years and know the place pretty well.