I don't think you will have a hard time getting a stage at all. I work in one of the high-end restaurants and we have a different stage almost every week. Some of the restaurants may assign you the grunt work, but some will give you an opportunity to see what each station is responsible for and sample several of the dishes. You will also get a chance to hear what the cooks there have to say about the other restaurants in town. This will help you decide where else to stage.
I see no reseaon why you can't aim for the top, if that is what you want. My approach was to get a temp job as soon as I came out here so I would have some income and have time to visit the different restaurants, arrange stages and not feel too rushed. This worked well for me, because I love my job now and am not in a hurry to move to a different restaurant.
Things in Vegas have changed quite a bit in the last few months. When the restaurants at the new casino, The Palazzo, started hiring at the end of the year, a lot of places lost cooks and were having a hard time finding applicants. However, now Vegas is getting a little jumpy about the economy and several casinos have had layoffs or hiring freezes. Gaming revenue has dropped slightly and hotel room rates are being lowered to keep rooms full. This doesn't mean that there aren't jobs available, but just make a plan to allow yourself the time you need to find the right job for you. If that means taking something temporarily to pay the bills, that might be a good approach.
As far as the restaurants you listed, here is what I know or have heard from people - Bradley Ogden is known for sourcing great farm-fresh ingredients. According to the various rating systems here (Mobil Guide, AAA and Michelin) - Robuchon, Alex and Guy Savoy are in the top three. Guy Savoy is the only restaurant he has in America, and Chef Stratta of Alex restaurant actually lives in Vegas and works in the kitchen. I have heard unpleasant things about working at Michael Mina, but that could just be rumor.
Best of luck.