Should I be moving my bell pepper plants into bigger pots now or should I let them grow more? If I should be moving them, how should I space them?
Their first 'adult' leaves are only just developing. I would wait until they've grown at least two sets (ie. 4) adult leaves. They will then be much more likely to survive the repotting.
Once they get a lot bigger than that, you'll have trouble separating them.
I usually plant outside and have about 18in (1-2ft) between individual plants. With pots I usually go for about 3 plants in a 12in pot - but they don't grow as well as in a bed with more spacing.