Some cameras do have a B&W mode as well as sepia etc but to be honest, I would rather take the photo in colour and then convert it because if you took it in B&W first then wished you had taken it in colour, it's not a problem.
I thought it might be quite useful to be able to view the pic you've just taken in b&w to make sure that it would look ok. When you're back at home tinkering with software, you may find that it needed to be taken again with different settings.
I'm not sure I would rely on a small LCD screen to show much more than lighting and composition, and if it looks OK in colour it will be OK in BW.
Any decent colour image will convert well into BW, and the extra detail captured by colour will make a better BW print too. I don't think that there is much that Photoshop (or similar) will not be able to do.
In addition, as already mentioned it's much better to have an original colour image for experimenting on.
If you want a simple way of converting to B&W take a look at http://www.jakerlund.net and download Johny's B&W Package V2.0 - its essentially a set of photoshop actions that coverts a colour image and gives some tint options via coloured layers. Simple and effective.
Their Edge Sharp v1.0 is good too - and a little more subtle than unsharp mask.