I'm not certain as to how truly "3G" the service is but both Globe and Smart offer a prepaid service which uses a modem to download a signal. I use Smartbro. Here's the link:
Home - Smart Bro
The quality of this cellular service varies from place to place. Smart's claims to speed are tempered by the following realities:
from almost zilch in Bayawan; to
approximately a true 300K here in Dumaguete.
The initial cost is 2500 pesos for the modem. Prepaid cards are available and the usage cost is 10 pesos per 30 minute units or fragments thereof. My much smarter than I wife sends me load, 10 pesos at a time from her cell phone. Naturally I buy her the cards for that in the first place. A symbiotic cellular relationship!
I find it a mixed blessing and use it as a bridge service. It is available anywhere you can get a cell phone signal. Thus I could check my E-Mail on my laptop under my mother-in-law's "tambis" tree in Bayawan. Here in Dumaguete, it is a truly mobile service, although inferior to my broadband at home or ubiquitous WI-FI signals elsewhere.
It's not everything to everyone - but it exists. I hope that helps.