Just back from Vegas and here is a brief report on the above:
Bartolloto - Lunch: food was very good but for the price we paid ($200 for two) the service needed much more polish. Service was prompt but the waiter had muck on his shirt, we were never asked if we wanted more bread, he could not pronounce half the dishes and he slopped wine on the table. We had fun, but it could have been much nicer.
Bouchon - the best meal we had in Vegas. There were 12 of us and service was prompt and very good. Food was excellent (the chicken was possibly the best I have had and my husband raved about the salmon) and dessert was fabulous (donuts with chocolate ice cream). Would not hesitate to recommend.
Binions - we were there for the fun more than the food. Traditional steak house with iceberg lettuce salad. Meat was excellent but WAY too much food. Service was good.
Diego - don't see much about Diego on chowhound but it is upscale mexican in the MGM. Food was excellent and the guacamole the best I have ever had. Margarita popsicles are a bit over-rated but are neat. Great service, good price.