I like the SE network and U+L in particular, hence this is my prefered site to ask a question. I am unsure if it is "okay" to ask about a xen virtualization related question. Any advice much appreciated
Questions about dom0 (at least if that's a Unix system, not sure if there are choices other than Linux) are fine.
So too, I think, are questions about the hypervisor itself at least if running under Linux or Unix. That's a part of many Linux distros, for example.
Questions about Linux or Unix guests are should be fine too.
Questions about Windows guests, probably not.
Alternative sites would be Serverfault (if you're using Xen professionally) or Super User (especially for those Windows guest questions) .
Note: This is of course just my opinion. Voting will tell if the rest of the community agrees.