I think street photography is part of people & portraits to be honest. If it's got people in it, then it's people, if not - then urban & architecture sounds about right..
pretty much covers it, yep - and if it's realllly abstract, chuck it in
creative where you can occasionally explain "your art" without too many philistines...
If the admins started breaking it down further you'd have even more diversity. Studio portraits, environmental portraits, candid portraits...
Birds, Brown, Birds Black, Birds White, Birds Green....
Cars Racing, Cars Street, Cars New, Cars Old, Cars Borrowed, Cars Blue...
where do we stop - the more "granularity" of the forum, the more chance you'll miss something good, and the less chance someone will actually see what you post and give meaningful critique on it - it's rare enough as it is these days...
Getting a new forum area is going to be a tough shout, every time there's a call for it discussed in the staff room, we end up in a discussion of how many other fora we aught to cull/combine as they're not getting enough footfall as it is...
My suggestion to the OP is simple - start a "Share your Street Photography" thread in the People & Portraits section, with another in the "urban and architecture" and maybe a third in "Creative" if you're so minded - add links to the "sister threads" in each, and make it clear in the first post that it's a group sharing thread, that all images posted are open for "robust critique" and see how it goes - if the thread hits 100 pages in a couple of days, we'll know that there's some real demand for it, and "da management" won't be able to ignore it...