Assembla is a good option. You can try devjavu as well. I've used both of them for a couple of years, devjavu has a cleaner environment.
I've seen 'SVN-and-trac in action' in two projects I've worked among with designers, project managers, people that had no previous contact with a version control system. They used the most common features without problems, I don't think it should be a big concern if your team could have a 2-hour training about the main concepts of version controlling with subversion.
EDIT:
There is a comparison page on this subject, it should be a good resource. In case it isn't, at least they have a large amount of links to svn hosting services. ;)
