Is hitchhiking on topic, or should I ask such questions at the travel-site? For me it is somehow outdoor-related, because I often travel this way to my starting points, druing the trip or back home, but I guess that´s not a typical association.
I think some aspects of hitch-hiking are certainly on-topic. Hitch-hiking is typically an activity in rural/natural areas, as opposed to urban ones. To be on the safe side you might want to bring a tent/bivouac, in case you don't get any ride by nightfall. Personally, I think it should be on-topic.
However, I think it is more specifically on-topic on Travel, and think you should expect better answers there, unless the questions are specifically on how to survive in outdoor conditions while waiting for your hitch.
From a US perspective, many thru-hikers on trails like the Appalachian or Pacific Crest Trails use hitch-hiking to make their way to and from towns for re-supply. (I suspect this is one of the few remaining circumstances in which Americans might regularly hitch-hike.) In this context posting to the outdoor forum is likely to garner more relevant answers, as the practice is both integral to the outdoor activity of thru-hiking and likely used mainly by such hikers. In regions where hitch-hiking is more common I suspect the travel forum may be more appropriate.