sweet and chillie peppers

They can be grown together as long as you don't want to harvest seeds to grow next year 

Is it best to keep sweet Peppers away from hot Chilli peppers when growing both plants

I'm inclined to go along with MoS advice if you were not saving seed for next year, but I can understand why you would ask - I've been doing a lot of research on growing chillies recently, and surprisingly a lot of (including some well known) chilli sites advise against it if you want heat in the hot chillies.  I can only think that someone suggested it if seed saving was important to retain the genes that make for heat, but along the way like Chinese whispers, everyone else has copied it into something else entirely.