Low end or high end of yeast t's

Is the low end or high end of the fermentation temperature better?

In my experiences I've found that belgian and ale yeasts work better at the higher end while lager yeasts at the lower end.

Keep in mind that the actual fermentation generates energy/heat and your beer could be 10 degrees warmer than you think.

It depends on the type of flavor you are looking for. Generally, the lower end of the range is best for most ales.

If I have one of those sticker thermometers on my carboy does that read the beer temperature (i.e. with the added heat from fermentation)?

Exactly- the correct answer is "it depends".

When I want a "clean", neutral taste, I ferment at the bottom of the range. When I want a fruitier profile, I ferment at the higher end of the range. For example- in the "Tongue Splitter" IPA I did using Northwest ale yeast, I wanted some of the fruitiness to come out from that yeast. So I fermented it at 74 degrees (wort temperature, not ambient temperature). When I did the same yeast in a different beer, I wanted a clean, non-estery profile, so I fermented it at 62 degrees (just a bit under the yeast strain's range, but it did ferment). This worked great!