is there any way to make it so that my factory fog lights on my 1990 laredo 4x4 will come on even when the brights are on, or even when the rest of the lights are off?

Of course there is, but you'd have to rewire them. You take the 12v supply wire from the fog light switch and connect it directly to a 12v source. Right now, it goee through the headlamp switch.

it that a hard thing to do?

Depends. Can you read a schematic? Do you have some basic electrical hand tools (wire cutters, crimping pliers, volt meters, etc.)? Have you worked on any electrical systems in a car before?

If you answered yes to these questions, I'd say NO, it's not a hard thing to do.

If you answered no to these questions, I'd suggest you find some help.