Guide, you are going to more often than not get asked point-blank; "Why do you think you need to know?"
If you can come up with a good answer (often this involves liquor, food or shiny-bits), then someone might let you in on things and teach you how to access the Beacons. It's not exactly difficult, but you do need to understand how they are set-up and organized. Once you know where to look and how to approach the things, anyone with the least smidgen of social telepathy can figure out how to pose a polite query and receive a meaningful response. Who knows, it might come in handy one day--you wouldn't be the first cityfolk who had to use the Beacons to send out a distress call when their raft got eaten by a swarm of glintmidges.
Of course, you might have saved yourself the trouble and just read the appropriate page in the River Almanac. But nah; that'd be too easy, wouldn't it.