Don't think it'll let you build in a dungeon. But your general reasoning is solid and agree it's a smart thing to do in the forest and mountain; you can still make this work.

I have portals and the crafting table (to build it and prevent nearby spawns) in relatively undefended but useful locations such as the middle of a copper mine or silver mine that I'm mining. It's quite useful as you'll collect huge amounts of stone while mining and this way you can immediately save all of it in your home base without affecting your ore collection.
Just make there are no enemies close by when you use it because if an enemy comes after you and you jump in the portal, it can target the portal and destroy it. But even if that happens, you're already running back and forth anyway, so you're no worse off.

If you want to be a bit more secure, just build a few walls around it or put it in a nearby skeleton tower, but that's not really needed most of the time.