Are there any good summer camps in Arlington?

To my knowledge, there are no summer camps here at all. You're not going to find too many right in the Poughkeepsie area as they tend to be in more open and rural settings in Dutchess County, though there is one up in Fairview called One 4 All (I'd imagine you can get there in 10-15 minutes from anywhere in Arlington). Aside from this, you'll have to go further away from Arlington to find others.