Went into Hidden Valley bunker early on in the game. Walked in there to investigate with ED-E but ended up ratting out the BoS to the NCR; killed some of the BoS guys that came running out. Now I'm getting towards the end of the game and I can't get back into the base. I've already been in there, so I know the passphrase, I just cant use it to get in anymore.
Using Veronica is out because she got snippy and was ended.

Other than lockpick 100 (Im level 27 now, probably too late for that), how the hell do I get in there?

You can't. I can't imagine not making a character without a 100 in lock pick.

If you can get the skill books and boost lock pick to at least 80 you can use a skill mag

If you have the comprehension perk, a lockpick skillmagazine and a utility vault jumpsuit you can give your lockpick skills a temporary boost of 25 points.
You could also go and find the Tumblers Today lockpick skillbooks. There's 4 of them in Fallout New Vegas and if you have the comprehension perk, the
4 of them will grant you a permanent boost of 16 points. And if you haven't used the 'tag' perk yet, that's another 15 permanent points you can add to your
lockpick skills.

So comprehension perk, skillmagazine, 4 skillbooks and tag perk is 56 extra points (of which 25 temporary).

The skillbooks are located here (from the wiki):

Silver Peak Mine -> Inside the shack, behind the two small tables, on the ground in an open locker, right of the entrance.
Bitter Springs Recreation Area -> Inside the office shack to the west, on the desk in the smaller of the two rooms.
The Prospector's Den -> Inside the caves, in the subterranean Den structure, in the large barracks room, on the floor in the far right corner.
Wolfhorn Ranch -> Inside the farmhouse, partially under the fridge without door.

Hope this helps, good luck!

When i was using veronica she was acting wierd and crouching while saying "see you arond"

What's your percent chance to force the lock? I guess you could just try this over and over, reloading every time you fail...

Thanks guys, I'll go track down the books and try to get my skill up.

Doesn't seem like I can complete "For the Republic, Part II" without cracking that lock. Means I'll have to level all the way to 30 before finishing that quest.

You can't force it if you can't even get into the little unlock minigame right?

If you are on a PC enter cheat mode, click on the door, write unlock.