The phrase "at plenty of" is not correct in standard written English.
It is likely a misphrasing of "plenty of," which is used to indicate a large amount or number of something.
Example: "There are plenty of options available for you to choose from."
Alternatives: "a lot of" or "many of".
"I've bought hair at plenty of other places," she said.
As the name suggests, you can break your journey at plenty of places along the way.
It's a short, scary experience that hints at plenty of potential.
For Mr. Bloomberg, the new polls released this week hint at plenty of weaknesses and opportunities.
Jacob, who is 33, had been shot at plenty of times as a boy.
Subjects like solar panels and smart-grid technologies have become a topic of discussion at plenty of Austin happy hours.
Plenty to look at, and plenty of people to talk to.
There's nobody on the street at midnight, plenty of parking.
In London and the South East at least, plenty of economic demand exists.
And at least plenty of them have mighty fine club careers to look back on.
There are, at least, plenty of unemployed bankers to choose from.
