I wouldn't say it's always the "elite" guilds. Big guilds (that aren't necessarily elite, as in they don't go through a lot of endgame stuff) have a lot of guild runs through UBRS and so on. In fact, those are the best guilds for running UBRS and the other non-raid 60 stuff, as they aren't going to be doing MC/ZG/AQ/BWL much, if at all. My old guild was like that... it's part of why the raiders from that guild split off and we formed our own guild, and are basically working on learning Nef at this point.
I'm kind of lucky in that I was in a guild in beta that planned on carrying over to retail. So I had a spot "reserved" for me when I got back in retail. Honestly, though, if you're trying to get into an established raid guild... either check the sites for the raid guilds on your server and see when they need warriors, or join a guild that's on the cusp and learn raid content with them... or, I don't know what else to suggest aside from finding a small guild and hoping you make some friends, and then when/if they split or merge with another guild for raiding purposes, hope they take you along.
Be prepared to get bored of raid content though. I've got a pretty good tolerance for repetition and it's still getting dull to me after 6 or so months of raiding. Though maybe that has more to do with the lack of raid dungeons (there's basically 5, though I guess there's also basically 5 regular level 60 instances...) than it does with the actual raid content itself. Anyway, if you get bored of running the same instances over and over again... it's going to happen just as fast with raid content, which is a large part of why I've been scaling back my playtime.