As I am totally new to Caching, this may be an absolute noob thing to say, but.......
Me, my wife, and Col. Angus ( the dog ), hit the park every Saturday. The same park, mind you, for the past 3 months or so. My wife brings a 5-8 quart sized bag with her. It is a mesh bag sold at Wal-Mart, or Target as a beach tote bag. I rigged a shoulder strap for the bag, and we run the dog, pick up the trash and get a few miles of walking in.
Again, the same park for at least 3 months, because there was soooo much trash, we still aren't done. She is up to 45 bags of trash I believe, posiibly more. I know she fills that bag at least 5 times each time we have gone. The bag is dumped periodically in the garbage cans in the park. Ohhhh yes, there are cans, they just fail to get used properly.
The kicker: I have read so far, that folks Cach in groups, big and small. Sooooo, why don't you designate 1 person each trip to carry some sort of trash bag. You don't have to lug it wround all day, especially if you are on a quick find.
Angus