If you really want to leave and come back for a better plan here, the cheapest I know of is Freedom's 5$ plan. But you'd probably need to buy a SIM as well, those are usually 10$.Or just look at other providers generally for something more permanent ...
I've not dealt with Virgin, but the longest it's ever taken me to port was about 30 minutes. It's odd that Virgin is saying 4 hours, but his number should still be good until it's ported. Then again, I've no idea how they work there.
