I work in radio astronomy, and our preferred distance to a town is honestly as far as possible! There are plenty of devices that can interfere with observations, from dog collars to toasters to electric blankets. There's an amusing story from the 1990s about a mysterious class of radio sources called perytons, which were eventually found to emanate from the open door of an observatory microwave!
Other folks have mentioned the Green Bank Observatory in West Virginia, which lies on the edge of the town of Green Bank. It's within the roughly 10,000 square mile National Radio Quiet Zone, but on the observatory grounds, there are additional zones, designated Zone 1 and Zone 2. In Zone 1, there are some extreme restrictions; for example, all vehicles must be diesel, as non-diesel vehicles can be strong sources of broadband emission.
In Zone 2, the measures are laxer for logistical reasons - the observatory does need things like microwaves and servers, though some are shielded where possible. That said, things like cell phones and Bluetooth devices are prohibited, and there is no Wi-Fi service (make sure your laptop has an ethernet port!). If you want to take pictures, you'll need to use a disposable camera. Some of these bans extend in a ten-mile radius of the observatory.
At the GBO, the primary 100-meter telescope is located ~1 mile from the closest edge of the observatory grounds, and a little further from the center of town - which, by the way, houses only a couple hundred people. This works fairly well, but that's partly because Green Bank is small and isolated, folks typically obey restrictions, and the RFI team at the observatory knows what they're doing (they do chase down violators if they can identify rogue sources).
I think that a town of a few thousand people - tens of times the size of the town of Green Bank - should at minimum be several miles away from the telescope. They would need to be okay without cell phones, with using ethernet connections and diesel vehicles, and minimizing the use of devices like heated blankets . . . and microwaves. Enforcing even normal NRQZ restrictions on folks who don't want to abide by them might be difficult, particularly if there are many out-of-towners who aren't used to the regulations.