Which institution? Most homeless shelters and mental hospitals don't allow recreational drug use or possession on the premises, and I doubt those policies would change even if drugs were legalized. And most drug addicts can't hold down a stable job to pay for private housing regardless of legal status.

I generally think legalization is a good idea. But junkies are always going to be a burden who live on the margins of society and survive by leeching off the rest of us (crime, welfare, donations).