I notice in a search for brake levers that single right levers are easier to come by than single left.

Using a 'safety brake' on a fixie i thought common practice was to put a brake on the left side for the front brake. Yeah I know it can go on either side but I thought that was the convention since people are instinctively used to pulling the left lever for front brake.

So, do people prefer left or right? (I prefer left for myself but I build bikes for others so I would like to get a consensus)

It's whatever that suits you, I've been used to left lever as front. I'm sure there are quite a lot of people who route their front brake to the right.

Different strokes for different folks.

Heck, route it onto the stem if that suits you.

I'm new to fixies, but i'm leaving mine on the left because I alternate between my fixed and geared bike.

(I prefer left for myself but I build bikes for others so I would like to get a consensus)[/QUOTE]
You answer'd your own question.

I spent years riding a motorcycle right side = front brake

Good luck!

Left side is probably a safe bet, assuming you're in the US, since that's where most people are accustomed to finding the front brake. But the right side is often a better choice - right-handed people have more strength and control, and it leaves the left hand free to signal the more important lane movements.

Best to ask each customer, or be ready to switch it if you're building bikes before you find customers.

Yup, everyone is nailing this one. For example, I'm left handed and do not ride a motorcycle. My left hand simply reacts faster and is more deft at modulating the brake. Left side all the way for me. Right handed people and those who ride motorcycles I think would prefer the front brake on the right. It's all about "no-brain" reaction time.

Both my bikes, geared and fixie, have front brake connected to right lever

All my bikes have the front brake on the right side. I do a few cross races now and then and it makes the moving dismount thing easier. I started with it like that on my Surly, and then figured if I had it like that on one bike, I better have it like that on all three.

I run front=left on my two-brake bikes and front=right on my one-brake bike. I got an XT caliper, right lever, and 8" rotor for $40, so I just went with it on my fixed gear 29er/cruiser. If there's only one brake lever, you're going to find it whether it's on the left or the right (and if it's an 8" hydraulic disc, you aren't going to need much hand strength).

I also think that the safest "safety brake" is a brake you use. Every bike brakes differently, and the more accustomed you are to your brake(s), the more effectively you're going to deploy it (them) on instinct. If you're never used your brake before and a dump truck pulls out in front of you, you may not even remember it's there (and don't get me started on stem-mounted/seatpost-mounted/top tube-mounted brakes). Bikes don't have ABS, so stopping yours in the minimum distance takes practice.