It's all very yeast-strain dependent, of course. But for American style ales I typically find a temp in the low to mid 60's is best - perhaps 63-65. Enkamania's recommended temp range is very frequently used by homebrewers to frequently good effect, and it does make a vigorous fermentation more certain. I personally would only go that high with most American strains if I were uncertain about yeast health and viability, as it doesn't always lend itself to a perfectly clean flavor profile.
The temps noted are fermentation temps, bear in mind. The beer itself can get a fair amount warmer than ambient temperature during active fermentation. I wouldn't complain about an ambient temp of 60F for most american ales if the yeast is healthy (i.e. from a large, active starter) though 63 is perfectly fine as well. If you do what the previous posters recommend and set a probe to track the beer temperature, then I would go up to at least 63.