I've been playing on Bovada for about a month, and while I do like the fact that it's more "pure" poker in that HUDs don't work on it, it's also very frustrating, because you really have zero reads on your opponents.

Given stakes of 05/10, and a table full of regs mixed with people making lots of stupid mistakes, what's the best way to handle this?

The root problem is that someone betting hard at you could have absolutely nothing (but believe that they do, out of ignorance), or you could be facing someone who knows what they're doing and are betting logically. Since everyone's just a number (no names are used), you never know who you are facing.

Is the solution to just stick to ABC and wait for good hands that hit the flop?

I play alot of 10PLO and I'd say alot of the gameplay is incredibly similar. Although I use PT and it is helpful for figuring things out - such as how the best best players play. I use the hud mainly to monitor my own play .
If someone is playing foolishly - they will learn quick or lose all their money - if they bluff you once - who cares !
Someone 3 barrelling like you describe at 10NL is almost always the nuts. They aren't good enough to think about what you have and rarely look past the current street.

My advise - is to worry about your own game - I have found so far that the best players at 10NL check when they miss and bet when they hit - it's as simple as that .

btw - just because they're regs - doesn't mean they are good.

Thanks for the feedback. I follow the "bet when you have it, check/fold if you don't" approach, but the part I'm struggling with is the marginal hands, where you've got something like bottom two and a queen-high flush draw. It's really hard playing those hands if you have no idea if your opponent is confidently betting a bare straight draw, or is confidently betting top set...

This. You should be able to carve out a decent win rate at PLO10 regardless of how your opponents play, so just work hard on your own game.