Hi,
As far as I can see the internal oscillator on the 12F683 defaults to 4MHz so I'd say you "should" be OK.
The best thing to do though is to actually measure it. If you have a scope or frequency counter then flipping an output in a loop at a "known" frequency will tell you if the PIC is indeed running at the frequency you think it is - and at the frequency you told the compiler it is. If you don't have a scope or frequency counter then a 1Hz blink should suffice to tell you if it's in the ballpark or off by a factor of two or more.

/Henrik.