Cerb, I was disadvantaged too and I applied disadvantaged on AMCAS. The above poster is right, because I applied to UCLA and they had a section to write if you were disadvantaged. UCI might ask the same question.
Although I don't know if it helped, I know that it was a topic of discussion in my personal statement. It came up in my interviews because I had written about it in my PS. If it was an important part of your path to becoming a doc, include it for sure. It can only help the schools understand your background. Also, I don't know this for sure, but I think it would be ridiculous for a school to reject you for not having the funds to pay for med school, since loans will generally cover everything (theoretically).
I am a minority but not URM, so I can't help you as far as URM status goes, but I know that some schools will applaud you if you had to work 40 hours/week to get through school while maintaining a high GPA and getting a high mcat score.