Because of the extensive nature of Boca Raton, taxis are not a good idea unless you are in a pinch. Prices would be hefty because of the distances as well, so you are much better off with your own form of transportaion. Therefore, when visiting Boca Raton it is definitely a good (if not absolutely necessary) plan to rent a car.
The top car rental companies in the area are:

Avis Rent A Car Systems, Inc  (561) 241-0705
Budget Car & Truck Rental  (561) 750-7369
Enterprise Rent A Car  (561) 852-0031