Since I work this weekend, here's a little help for some others:

The McDowell Sonoran Preserve (no Geocaching allowed) is only a very small part of the McDowell Mountains.

Here's the Scottsdale website:
http://www.scottsdaleaz.gov/preserve/currenttopics.asp

Here's the official map:
http://www.scottsdaleaz.gov/preserve/pdf/overview.pdf

Most is actually a part of the Maricopa County Park System.

Here's their map (it's part topo):

http://www.maricopa.gov/parks/mcdowell/pdf/McDowell_color.pdf

Plan your entrance accordingly, but there is a standard county park $5.00 admission fee. This park has famous mountain bike trails. It could be a bonus if you pack the Trek (like Lance).

Good luck. Hope this helps!!