We were in Nassau from early morning until Midnight. We took Bus 10A to Breezes ($1), walked up to the front desk, and bought day passes ($60). Entitles you to all-inclusive privileges from 10 am to 6 pm, and it was really nice. We met others there from RCL who had paid $87 as an excursion, but they didn't arrive at the resort until after 2 pm. Boy, were they MAD, and who could blame them!
If you decide to go consider taking a taxi there; the bus takes a round-about route to Breezes (about 20-25 mins), but you can catch it right out front to go straight back into town (5-10 mins).
FYI, the downtown shops, etc. close at 6:00 on Saturdays. We had planned to do our shopping then, but had to tough it out at Sr. Frog's instead.