I'm playing Fallout 1 over again and this time I made it to Mariposa without getting bored.
Now, I'm in level three, haven't used the computer in level 1 due to playing a stupid character, and ain't got a radio either.

I'm there where the cells are. I used repair to get myself in (was surprised that it worked) through the yellow forcefield, and killed the two mutants plus the chick who cried the other mutant.
There I am. Stuck between two yellow forcefields. I accidentally saved over and now there is no points o' return.

I googled a bit and found out that using repair to the hourglass-shaped parts just aside the forcefields should open them.
I used tool to it and message came that I had disabled temporarily the force field emitter.
But the forcefield itself didn't open.

Been a bit since I last time played thru the game.

Your problem (I believe), based on my last playthough which was about 4 weeks ago, is that the tool - whilst increasing your chances to repair - doesn't affect forcefields, even when you're successful. Could be a bug, not sure what it is. I came across it as I was escaping with a self-destruct timer (yikes!) but I thought I'd start doing it with my bare hands again, and whadaya know, it worked I escaped in time, everyone drank lemonade, it was magical.

So give that a try, it might take you a while if you're not amazing at repairs (and if your character is 'stupid', though not sure how much that would affect it, if at all), but it should work eventually, and when it does work, it should 'actually' work Only for a few seconds mind, so run!