I'm thinking "low yield" means your 1 month away rotation doesn't help you all that much in terms of matching at that program.
Maybe the program doesn't take much stock in knowing you. Maybe they go for scores, grades, research ....
At any rate, pretty much all the West Coast / Mountain State programs are pretty competitive. The 50+ top notch applicants who are all dying to get into UCSF have to have their back ups you know. Same for UCSD, UCLA, U Wash, Oregon, etc.
Some of the supposedly less competitive West Coast programs have only 3 or 4 spots. After 1 spot goes to a local med student and 1 spot goes to that great applicant who did an away rotation there, you don't have the best of odds.
I'd roughly guess upper 230s on step 1 and a solid app otherwise could give you good odds of matching out west somewhere. Apply everywhere and make sure the programs know you really want to stay / go out west.