I found three at Travelocity that are within two blocks walk down ocean drive and arent very expensive. Bear in mind this is South Beach so you arent going to find $40 hotel rooms.
Check out
Beacon Hotel – Aprox $140 a night located right on Ocean Drive and a very nice place actually. http://www.beacon-hotel.com/
Avalon Hotel – Ocean Drive – $130 a night. http://www.avalonhotel.com/
Blue Moon Hotel – On Collins ave, but still only two blocks away. This one has a pool $144 a night. http://www.bluemoonhotel.com/
Another option is to do what many of us did the first year of the Spring Break, split a room with another CAP member. Its fun and it cuts your costs in half. The other benefit is you stay at the Loews which is an incredible property loaded with ammenities.