I know how you feel, it's overwhelming in those parks. Makes you wonder who the jerk was that dropped pull tabs everywhere, doesn't it? USE THE TRASH CAN! Seriously though, I would stick with the Vaquero since I don't think your problem is specific to the Vaquero. Seems like if you are finding clad dimes and quarters you are doing good. With discrim just above tab, you should find most of the good coins as long as they're not too deep. You probably find pre '82 pennies too, right? Who cares if you miss the zinc pennies. As unfortunate as it is, it may be that you just have to give up nickels and gold b/c of pull tab/foil heaven. That is unless you want to dig a hundred holes for one nickel or a thousand for a ring. I don't think this is a problem with just the Vaquero - I think that's just all detectors. Even my "top of the line" target ID detector flips out in trashy parks.
I use a Tejon with a 5.75 concentric and discrim just above tab in a very trashy park from 1880, and besides new dimes and quarters, I occasionally come across a wheat or silver dime and very little trash. The 5.75 is the reason. I totally 100% recommend that you try the 5.75 concentric coil with the Vaquero - it will get you where you want to be. Good luck,
Ian