Also check Expedia. That was how I got a fabulous rate at the Tropicana when we stayed there. That was awhile ago (Feb of 06) for a last minute trip, but my rate was around $60 a night. When I checked for October trip, Expedia was cheaper than what I found from Tropicana's online booking thing. I didnt' even know that they had an ENT rate.
The Tropicana is great, we loved our stay there. Very nice staff, super clean room and bathroom and the staff were so nice. And the location. It also had a free breakfast that while minimal, was way better than some of the other free breakfasts I have had on Harbor.
Hope you get a great rate!