In a bed where you pull the weeds and grass they probably will do well with a row in the middle. I plant everthing in my garden 30 in wide so I can run the tiller down the middle till the plants get really big.
I thnk 2-3inches is too close. I drop bean seed about 3-4 in spacing and if all germinate, thin to 6-8 in.

In my bush bean patch, I noticed I have a few really heavy producers, and they are the ones growing next to a "bare spot" where I had to pull a diseased seedling, or at the end of the row. It makes me think I should give them all more space next time. Exposure to sunlight from top to bottom may be the key, I don't know. Mine were planted about 5 inches apart.

Thanks! The lettuces haven't all given up yet, so I think I'll stick with the 30 inch spacing for this year. Most things do well with a little extra room anyway, and this way I can reach in to pick from either side without crowding.