Patty, I haven't nailed it down precisely, but there is a large roadcut on NM Highway 4 between Jemez and Bandolier, in the Valles Caldera area, right before a picnic area, where I stop to pick up chunks of obsidian when I'm on my way through. It's on public land, at one time it was National Forest but since then I think the land was added to the Valles Caldera National Preserve. I found a 2021 article about the general distribution of obsidian in the Jemez area. Rhyolite and obsidian are the focus of this map and article. Here's an NPS report about the Valles Grandes history that might be a long evening of reading. When I drove through in the past it was still the Santa Fe National Forest, now it's the new NPS site. Still, picking up rocks on the highway would probably go unnoticed. This account from a blogger who went collecting in the caldera (from 2012). NPS rules - look, don't keep. But they aren't searching cars or people, is my guess. It's not like Petrified Forest where they do sometimes search vehicles. Anyway, as large as the Jemez obsidian range is, you should be able to find USFS or other land where you can pick up some. This document from the American Geophysical Union website says

Obsidian is pretty common in the Jemez Mountains, particularly in the Banco Bonito rhyolite. Once you leave the Valles Caldera (a National Preserve), you’re in the Santa Fe National Forest; casual rock collecting is allowed, as long as you’re not carting off massive amounts of material (no more than a bucket per day). The best place to find bits you can legally collect is in the East Fork of the Jemez River, which you can get to using the Las Conchas trail.

(I should also say "stop me if you've heard this before" - I know we've talked about rocks and places to pick them up.)