I would like a idea on how much to do acid etch concrete stain on a patio.

I know there are a lot of variables but a BASIC idea of how much, done by a contractor would be adequate.

12x20 area... basic one color, no cutting lines into concrete, just stain it one nice marbleized color...

The best way to find this out is get 3 bids for the work. Your site conditions and Geo will effect pricing. Keep the guessing out make the calls and then you have concrete prices for the scope of the work

I agree, get 3 bids but also consider doing it yourself, this is a not a rocket science project. How to Stain a Concrete Patio | eHow.com