Driving around and looking for places under constuction is a great way to find places and also try looking online under your counties civil works department or calling them , they may be able to point you in the right direction.
Or you could stop and ask poeple at a constuction site and see if you can do it there after work or if they know of a good place for you to try.
Good Luck - HH
P.S. If you stop to ask the construction workers, dont take it to heart if they run you off, they are very stressed out alot of times and may get a little short with you, if they do just leave and go ask the guys on the next site.
Try to find the guy who dont look busy, he will be a little more willing to give you his time and consideration.... and be polite !!!
You catch more flies with honey than with vinegar.