If you want to go fairly cheap, The Comfort Suites, located directly across the street from Atlantis, a great way to go. The rooms are mini-suites, with a small kitchenette and you get the exact ground privledges as almost all the Atlantis guest. You just don't have access to the one private beach/pool area that only the most exclusive guests get to frolic in.
Meals at Atlantis are freaking crazy. A simple breakfast will run you $35-$50. CS has a shuttle to a local food market where you can buy foodstuffs for about twice the price you are used to, but are still a fraction of the price of a meal.