Truck for sure. You won't get nearly as much in trash cans, trust me. For some reason, it doesn't compare. You'll load much more into a truck bed. It'll leak out the back, but no worries, not a big problem. The only tough part is that getting out is sometimes a pain, but hey, for a sesh, its worth it.
Me and my friend do this all the time. If you happen to only be available at a certain time and you're not sure whether they're dumping or not, go in, be polite, and ask them too. If they're not super busy, they'll dump whats in the hopper. We did that once, and I was soooooooooooooo stoked.