All three providers, Viva, Claro and Orange now have prepaid data plans.
Claro:
BlackBerry - BIS services mail, social, light, full/unlimited
Other phones - Internet Movil
Orange:
BlackBerry - BIS services unlimited
Other phones - Orange Net
Viva:
BlackBerry - BIS service unlimited
All can be contracted on prepaid basis. With Claro and Viva you can get plans on daily, weekly and by-weekly plans.
You will get 3G with Claro, 2G only on Viva. You will get 3G on Orange ONLY if your phone is from Europe because Orange picked up the rariest of the bands for 3G - 900 Mhz used only by a few European operators.
Viva connections suck, you get very bad quality 2G EDGE connection, browsing will be somewhat bearable in off peak hours, in peak hours it's virtually unusable. No streaming, youtube or tethering on Viva. On Orange and Claro you can stream vides, audio, youtube etc. And also use your Blackberry as a modem (tethering).
Again, if you did not buy your 3G phone in Orange in the past 12 months, you will most likely not be able to access 3G on Orange. Even if you bought a 3G phone from Orange but you bought it before Orange launched 3G then most likely it is not compatible.... Yes, Orange sold in the past lots of 3G phones (Iphones, Blackberrys etc.) that are now not compatible with its own 3G. Also many 3G phones sold in Europe possibly may not be compatible with Orange 3G because Europe uses 2100 Mhz band which is present both in American and European versions of 3G phones (e.g. Blackberry curve 9300 or bold 9780 or torch 9800). Many European carriers sell American versions or have many on stock simply because the frequency band they are using is present in both versions. Most likely to use 3G on Orange you will need to buy one of their newer 3G phones. .... Good way to make some money on phone sales as well.... Good bye Ebay for Orange
According to both Claro and Orange, the Blackberry BIS plans are truly unlimited and there is no degradation of speed or download limits, even on 3G.