I'm willing to wait...sometimes.
For example, Final Fantasy VIII is one of my favorite games, and usually, partially by choice, I barely get a fight in within the first 2 hours! It's like, there's not that much forced dialogue, but there's a lot of optional stuff to do from the beginning. Talk to everyone in the place you start. There's a minigame you can play already, and it's good fun. The game has a wealth of information you can access from the menu, and some from a terminal in some rooms...most of it background information and gameplay tutorials. I manage to spend a long time doing this before getting to my first battle. But you know what? I love it. Battle is not the only gameplay in RPGs, you know. Plus, the game actually "starts" with a battle. A movie scene showing you a fight...not the same thing I know, but it almost feels like you fought a battle right away...
But that's a special case, and definitely not an RPG Maker game.
I'd say it depends on the tone and length of your game. If you have a longer game, I wouldn't mind waiting longer to fight. But some people might get bored of waiting.
I personally, tend to have a battle ideally within the first 15 minutes or so. I say ideally because I've never fully finalized an intro for ANY of my projects!
I do have an RPG idea that starts a battle IMMEDIATELY when you select New Game. Like the battle effect "whoosh" would happen as soon as you start. Maybe, use one of them scripts that lets you skip the title screen if there is no save file, and it's like BATTLE IMMEDIATELY. As soon as you open the game the first time, that would be interesting. SaGa Frontier 2 actually sort of does this, but it's a computer controlled, quick battle. Speaking of SaGa Frontier 2, it starts out rather slow battle wise if you follow Gustave's story first. But hey, the graphics are great, the music is beautiful, and the basics of the characters and plot so far is interesting enough (and a heck of a lot happens story-wise for young Gustave in the beginning)
Also, one of my RPG projects, I felt would start a little too slow for the main character, so I threw in a prologue battle using really high level characters doing some super important battle in the beginning. There'd even be dialogue during the fight, so it's not just BATTLE first.