If you dont find anyone on ST, check here

http://www.arizonaroadracers.com/

if that doesn't work, I'd call Runners Den, someone there should have some routes.

There's something called the "Greenbelt" that may be made into 20 miles out and back, but i'm not sure. It is sort of a mixed use recreation sidewalk, but some of it meanders, so i'm not sure if you're interested.

A good, easy, flat run would be to start at Scottsdale Running Company, SE corner of Hayden/Indian Bend Road, and take the canal west/southwest. There is a wide dirt path on either side of the canal, and it goes forever. You can find a distance calculator for that starting location on their website: http://www.scottsdalerunningco.com/arizona_canal.html

For a 20 mile run, you would turn around at the Arizona Biltmore Resort or 24th Street. You will find water fountains at the park on the south side of the canal at 56th St, and at the gas station at 40th St. Otherwise, you will need to be self-sufficient or creative on the water sources. PF Chang's Marathon is in January, so there should be lots of other runners, although they may not be up to 20-milers yet and many do long runs on Saturdays too.

Thanks much... very helpful!

By the way, the canal is south of the shopping center where Scottsdale Running Company is located, and you could just follow the golf course and greenbelt concrete paths underneath Hayden, heading west, until you find the dirt canal path heading southwest. There may also be some construction around the canal by downtown Scottsdale (3 miles in), but you should be able to follow the canal without too much trouble.

Have fun!