Is this your first time in San Juan? It is completely safe to take a taxi from the airport at that hour, and later. I say that because obviously it is not true everywhere! If you expect to be tired I'd just recommend you find a hotel in Isla Verde (there are many!) and take a cab there when you arrive. Cab fare should be less than $15. I would not recommend you stay in the airport hotel.
One that looks nice to me every time I pass it is the San Juan Water & Beach Club (~$130 on hotels.com), but, as I said, there are many options. I would avoid the super-budget ones such as the Villa Verde Inn or the Coqui Inn, which are on the other side of the highway, but that still leaves you with a ton of choices, and if you are coming soon (i.e., the summer) you should be able to find plenty of deals.