I previously worked in transfer and non-traditional admissions at a highly competitive, top 25 private liberal arts college, plus I was a transfer student myself, and I also organize one of the largest annual transfer fairs in the U.S., so maybe I can give you some input. (By the way, regarding some of the comments here: Ouch! I promise, we higher ed people are not that evil. :))
First, this might seem like a silly question, but are you positive you were at the right open house? Most colleges and universities hold separate open houses or information sessions for traditional students, transfers, and non-traditional students. If you were getting looked at strangely and didn't see any other non-traditional applicants wandering around, it's possible you were at the wrong event. It happens, and most colleges will still try to accommodate you at the open house you do attend, but it might explain why they were a bit confused by your presence. Check to see with their office about events specially catered to non-traditional students.
That could also explain why the table for non-traditional students was poorly staffed. They may have set it up as a "just-in-case" table and stuck a student worker there to staff it. (We used to do that in case we ran into similar situations.) I can almost guarantee you that they didn't tell you about all of the services available for non-traditional students, so you might want to go onto their website or call your admissions counselor to learn more before you assume nothing else is offered. If you don't know who your personal admissions counselor is, check their admissions website for a special section for non-traditional and transfer students, or view their "Meet the Staff" page (if applicable) to locate yours.
Colleges that offer non-traditional lounges are usually ones that either do not offer non-traditional housing or offer only a very limited amount. That is an inescapable reality that you'll just need to accept now -- you may not get on-campus housing. And if you do get it, you may be one of a very small number of non-traditional students on campus. At colleges with relatively small non-traditional student bodies, most don't want to live on campus because it can be very awkward for them. At the college where I worked, about 10% of students were non-traditional, and of those, only about 20% chose to live on campus. They had one floor of one rather isolated dorm dedicated to them, and there was usually a wait-list involved. So if on-campus housing is essential for you, you'll really want to consider the percentage of non-traditionals living on campus, what the housing options are like, and what type of social expectations you'll have. (Related note: When you said you didn't want to take another tour from a freshman...another thing to accept now is that most students will indeed be 22 and under. If that's going to bother you and you're not going to want to hear about teenage concerns or wait for them to catch up on certain things in class, that's probably yet another reason to consider an institution with a greater non-traditional presence.)
Finally, there is one big difference I've noticed between traditional and non-traditional students: Traditionals approach open houses and other admissions interactions like they're being interviewed, while non-traditionals feel like they're interviewing the college. Traditionals ask questions and have a general attitude about them that's basically, "What can I do to impress you?"; non-traditionals can have a more demanding presence, as in, "What can your institution do for me?" There's no right or wrong way, of course, but I think that the more blunt, at times even harsh approach that some non-traditional students take can be momentarily jarring for admissions reps, because it's not what they're used to experiencing 99% of the time. They're not judging you badly for it; they're just going to have to take a minute to adjust their approach. When you described your first interactions, that came to mind for me as a possible contributor to your experience. Admissions reps pretty much expect students to come up to them, introduce themselves, say which program they're interested in, etc. So if they were giving you odd looks, it was probably because they were waiting for you to extend your hand and say, "Hi! My name is Billy, and I'm planning to apply as a non-traditional student in the ______ program for the Fall 2011 semester." That's kinda expected of everyone, not just non-traditional students, so you might be assuming you were getting the cold shoulder due to your age when, in reality, it was probably more of a presentation thing. :/
If anyone has any questions about the process, wants to know why certain things are done certain ways, what types of non-traditional services to look for, etc., please let me know. :) I'm so happy to see so many people who've gone on for higher education!