Yup, you just need to use the closer value, all timing will be slightly off, but in many situation it doesn't really matter. However SERIN, SERIN2, DEBUG and all bit-banged will not worrk as expected, nothing you can really do with odd OSC value, however with HSERIN/HSEROUT you can calculate the value of TXSTA/SPBRG (using PicMultiCalc) and specify them in the according DEFINEs, then your baudrate will be spot on.

Same goes for HPWM.

I2CREAD/SHIFTIN/I2CWRITE/SHIFTOUT are synchronous routines... no problem at all if the timings are a bit off.

hth