Just saw a video of someone exchanging a bike at a busy WaWa, and the guy jumped on the bike and rode off. Being in a busy public place does not protect you at all.
Besides, the cops have to get close enough to sniff you, and they aren't bothering with a couple of locals in the parking lot handing a guitar back and forth. You'd have to walk all the way out there, and that sounds like work, where are the donuts?
And besides again, it's the 21st century, nobody gives a shit about weed. If you're that paranoid, maybe you should cut back a bit. I've probably smoked your weight in weed, and I've never been that flakey about cops.