Have you tried talking to the owner/manager about free weights? It might not help, but if they find out members are interested in them they might consider getting some.
A generic 300 lb weight set and a
high quality power rack wouldn't really put them out all that much, at least not compared to any of the one/two function machines they already have.
How heavy are the available DBs? A lot of this depends on if they are heavy enough to challenge you, because you can do just about anything with DBs (except
heavy squats...unless you have some freakish cleaning ability.)
If they don't supply DBs that are heavy enough you may have to rely on the machines, which is fine if that is all you have available. That or you quit and find a gym with more free weights and a power rack. Depends on what you are happy with, personally I would find a gym with the barbells though.