What does treat 'em and street 'em mean?
As Hellion already mentioned, it's about medical treatment.
I believe it's used primarily in the U.S. where you're not covered by a national (or otherwise common) health insurance. If you lack medical insurance, the hospital is only required (by law) to treat the critical condition, and may then release you.
I believe it means "give them (medical) treatment and then get them out of the facility [and back on the street]."
it is an emergency medicine term meaning to quickly treat them so that they can get out of the emergency room quickly. It has nothing to do with insurance or inadequate care. it just means get their treatment done quickly so they can get out of the hospital