Hi, Dr. E and welcome to TNet and the wonderful world of Ace 250 detecting!
If you're finding poptops and bottle caps, you're well on your way to finding coins and stuff!! Believe me, most of the photos here are taken ONLY AFTER digging probably 50-100 pieces of trash!

And that's by the folks who have been doing this a while (not me, unfortunately!! LOL)
Best thing for you to do is just what you've been doing......get out and use your Ace. Dig it all. You'll start hearing subtle differences in tones in it and recognizing them and what they mean before too much longer. It took me probably 4-5 weeks using my Ace 3-4 times/week to start saying "OK, that's a deeper tone and not the dingdingding of a penny or dime. I'm gonna pass on digging this one." or "Hmmm, this is kinda strange sound, not like penny, not like dime, it's worth digging."
One thing that helped me was getting to playgrounds, not just parks. The parks in my area were pretty hunted out, so I needed to find places with GOOD signals.....clad coins, in my case. Playgrounds at parks, playgrounds at schools, playgrounds at playgrounds.....even the local boys club work well. Find places that haven't been hit too hard (yeah, I know, no place is ever totally hunted out, but there's a bunch of places that are REAL clean!)
Anywho, keep up the beeping. It'll come in time. And anytime you drive or go anywhere, look around and wonder to yourself "Hmmmm, where could someone have lost something that I can find??"
HH, ya'll!
Kajun