FlyI4,
If you are driving from the Northeast to AZ you have many ways to travel and if it was me I wouldn't bother going to the San Juan as my first choice. If it was me and I wanted a fairly direct route I would route thru Kansas and get into Colorado and fish there for a few days. You can then take I-25 from there down to Albuquerque and catch I-40 into AZ. Although the San Juan is a tailwater and the temps of the first stretch of the river remain relatively constant the air temp will be hot compared to streams in CO plus I personally think that the San Juan area is a hole (there's even an oil well in the river bed if I remember correctly). I think that you should definitely fish it some day because of the huge fish but between here and AZ I personally would pick other spots to check out.
Since you are going to be in AZ you should pick up Charlie Meck's book on the streams in AZ. I also recommend streams in NM such as the Rio Hondo and Cimmaron (near Taos) and the river systems in the Jemez river drainage- there are many mountain streams in NM and AZ that you can find less pressure and better scenery than the San Juan. Also there are some monster fish in the lakes up in the White Mountains and you should try to catch some native Apache trout while you are there.
Of course if you are going to school in Tempe you should ignore all of this advice and just fish the Salt river.
azcat