I have an ASA that is connected to my 3750 stack. I don't see any bpdu's being received on that port. Is it okay for me to enable portfast on this port? Should I enabled bpdu root guard if I do?
Yes you can enable portfast on the interface facing the ASA but it's always a good idea to have at least root guard enabled as the ASA does not support spanning tree.
In router mode BPDU's will not pass anyway as it's Layer 3, in transparent mode BPDU's will pass.