Prepaid phone with internet - 4 days (17-19 july) (San José)

Dear all
I would appreciate your help with some guides related to obtain a prepaid cellphone with Internet to use as GPS for my travel around Costa Rica for 4 days. I will rent a car and go to Volcan Arsenal, Poas and Manuel Antonio.

Please which is the faster way to obtain it fr the airport or close to it. And if any one need a ride to any of this place let me know. I will be from July 16 to 19.

Thanks in advance for your attention!

Nelly