Where to stay?

I think you are going to have to 'give' a bit more information if you expect any sensible replies to a question like this...
What sort of standard do you want?
Are there any definite 'pluses' you want or 'negatives' you want to avoid.
What sort of price range are you looking for?

As far as 'guest friendly' I have never heard of any hotel in Udon making an issue of that, although I do understand that one place is now charging for guests going to its customers' rooms as it had to engage extra 'security' staff to enable this safely.

There are plenty of hotels listed on this page with location map: http://www.udonmap.com/en/udonthani-bus ... ation.html

Udon Star on Watanan Road, opposite the Sampantamit Road. So central. About the same quality as Irish Clock or City Lodge - with about as many rooms - no pool..
Frankly if I wanted to stay that close to town centre I would save myself 500 baht a night & stay in the Top Mansion.
All that area is subject to noise & dust at the moment because of the redevelopments.
For about the 1,000 for central Charoen is a good bet as any & has the huge advantage of Yellow Bird as part of it.
If want luxury then really only the President & Prajaktra are in that market. Although it is a tuk tuk rather than a walk to the 'hot spots'. Either are probably well worth the extra for only 4 days....but, as I said before, we are flying on minimum data here..