the closest field to downtown vancouver would be north shore paintball. it's right across the lions gate bridge. costs $10 for entry and all-day air if you've got your own markers, $20 if you're renting. paint is $45 for 500. yeah it's a bit steep, but that's how it is lower mainland. there are group rates if you've got 12 or more people, though.
they've only got one field, and it's woodsball oriented, with stacks of tires and plywood forts. but i guess you don't have much land to work with if you're trying to get as close to downtown as possible. your other options are way out in surrey or maple ridge.