Cellphone for Three Weeks?

Will be traveling in Quito, Cuenca, and Guayaquil for three weeks. Please give advice/suggestions on the cheapest way to have a cellphone for 3 weeks. I would use it to call in Ecuador and recieve calls from the U.S. I would really like to get it at the UIO airport when I arrive.
My own locked iPhone international roaming is around $2 a minute.

There is a cell phone rental place in the terminal, however, they'll probably "rob" you (I mean prices). Here is what you do: right in front of the airport, there is a small shopping center called CC Aeropuerto. There are some electronic stores that sell GSM chips. They will work in your iPhone. Buy a chip, any provider: Movistar or Claro, it comes with $3, load another $5 on it, total would be $11-12, and enjoy! Incoming calls are free for you. The money you load on the chip never expire. The cheapest new phone would cost around $40 here...
Good luck!