How do I keep my cucumbers from being bitter

I think it has something to do with the plants not getting enough water. You could also look into getting your soil tested for having too much sodium or sulphur, also your water, some plants like filtered water better, perhaps you could buy onr of those britta (sp?) pitcher water filters, so when you water with the garden hose fill up the pitcher and it filters for you.
Also certain types of cuc's are for pickeling and the breed is naturally more bitter. Try the next time you buy seeds on-line to ask the help people which are better salad ones.

Cucumbers turn bitter if they are picked too late. The cukes that are left on the vine to get huge will always be bitter. It is better to pick them too soon then too late. Too soon and you just get a small cuke that still tastes good. Too late and you get a big cuke that tastes aweful.

Exactally what tadita said I usually pick mine before they start getting fat. Also I grow the burpless cukes