Yeah, I believe all the analog inputs are on PortA. Check your spec sheet.
The output impedance of the ADXL devices is 32k ohms, at least the ones I know. That is FAR too high to provide to a PIC which needs 2.5k ohms max to live up to its full specifications.
Also the ADXL devices need to be band-limited. Simply put a cap on the output, the cap will make an RC filter with the internal 32k output resistance to make a lowpass filter. You want to get rid of not only the noise but any signal made from vibrations which are undesirable to capture.
What is the purpose of the input on RA0?