Should I Include Braille?
Yes, short braille instructions (for initiating the speech mode) are needed. Most modern ATMs do a good job with this, so look for that braille the next time you use one.
That said, a PIN pad (as a stand-alone device) probably does not physically have space for even a sentence of braille. In that case, an exception for fundamental alteration would be applicable to the braille instructions. It is recommended that PIN vendors provide laminated braille instructions that could be made available upon request, but that goes above and beyond the explicit regulation.
On the other hand, a self-service grocery checkout lane could find the space for a sentence or two of braille instruction. The fare vending machines for DC Metro incorporate braille.