The taxi rates are all structured from the airport, and the pier is in one of the farthest zones in old san juan...I think it would be $25 or so, but don't quote me. I remember it costing me $15 to go to the condado which is about halfway in between. The radisson ambassador is OK...usually good rates available.
I actually thought the airport was nice...the terminal I landed in (United) had just been renovated (Nov '01).
The Wyndham is the hotel everyone talks about in old san juan near the pier, and it is a nice property, but pricey.