Hi Coco_Nut: WashU is by far more supportive of people who want to short track. They have a PSTP which is basically a short-track program + lots of financial perks to recruit people to short track and prepare for academic careers. This seems a very well-greased machine.
UCLA on the other hand has a program called STAR, however you can not apply to it until after your internship year. Most people in STAR do not short-track; a few that do have to get approval from the PD, who is known to deny someone shorttracking in the past and does not appear very suppportive of the idea of fast-track. In the past 5 years they have from 0 to at most 2 entering the STAR and only one or two in all those years were allowed to short-track. They have a very interesting system that you do not apply to STAR until your PGY2 instead of the intern year. So in effect it's the same as the regular fellowship, just that in this case you have more support for research and membership in STAR (for whatever that means).
My conclusion: WashU is a wonderful choice for people shorttracking, UCLA is not even close to that. Hope this helps. Happy ranking!