Taxis meet arriving planes. If you take one, negotiate the fare with the driver first, because cabs are unmetered here.
There are branches of Avis (tel. 787/832-0406), Budget (tel. 787/832-4570), and Hertz (tel. 787/832-3314) at the Mayagüez airport.
Note: This information was accurate when it was published, but can change without notice. Please be sure to confirm all rates and details directly with the companies in question before planning your trip.