No, there's not way to shorten the execution time (in instruction cycles that is) of a GOTO. What you can do is to "lengthen" the time of the other instructions.
Code:
Head:
PortA.2 = 1
@ NOP   ' Two nops to compensate for the GOTO
@ NOP
PortA.2 = 0
GOTO Head
Obviously this will also change the frequency.

/Henrik.