Cycling to Tucson

What distance are you shooting for?  I ask as it seems Tempe to Tucson requires a ride back (?or is it an overnighter with a return the next day?)  If you want 140ish miles and a safer (as in less cars) you may consider Tempe to Wickenburg (approx 145-160 miles round trip depending upon start place)  This gives some nice Carefree Hyway and US60 biking.

I have done that ride a couple of times from a couple different angles. Like Jerry said, it depends on the goal. I have in-laws down there, and it's a nice 128ish miles from my place in Dobson Ranch down to theirs in Rita Ranch (far south Tucson), so it's easy to bike down and get a ride back.

The best routes between here and there are on the East side of I10. Here are a couple of my maps:

Casa Grande to Saguaro 300K brevet:
http://www.beginnertriathlete.com/discussion/training/map.asp?routeid=38220

'08 Gaba Century:
http://www.beginnertriathlete.com/discussion/training/map.asp?routeid=39627

My home-to-inlaws route:
http://www.beginnertriathlete.com/discussion/training/map.asp?routeid=45332

You can see the gist in all three on how to get down there. My only advice is once you get down to Oro Valley, avoid the west side of I10 and downtown Tucson. The roads are HORRIBLE.  I did it to avoid the 30mile false flat climb in the Brevet map, but if time doesn't matter I'd head down the Eastern route and make the climb up into Oracle or else turn east on Tangerine and head up there. 

Feel free to ask more questions since the maps only give so much detail.  For instance, There are frontage roads along I10 from Picacho down to Oro Valley, but the map looks like I'm riding on the freeway (don't do that )