Use digital in 14. It corresponds to pin RC0 on the PIC, which coincidentally is the clock for Timer 1/3 when they are used as (a)synchonous counters. Look at the PIC reference on
www.kevin.org/frc Specifically, look at the TIMER section and the PORTC section. Note that I haven't tried this yet, but this is how I'm planning on doing things. You can get pretty good resolution and update rates since the max frequency is 50kHz, and you just sample it and clear it every PID loop, so you don't have to deal with the variable update rates of some other methods. Best of all, no interrupts needed.