The key to your request is the following (imho):
The load can be between 0 and 20 amps. I would like to be able to monitor the current in to the PIC.
If you want to monitor current from 0 to 20A (both ends inclusive), then the Allegro parts are probably best.

However, if all you need is to set a reasonable trip point (e.g.) 10A at which an overcurrent signal trips; then a sense resistor followed by some form of a comparator is probably easiest and less expensive. We have normally used something like the LT1787 with multiple parallel power-rated 0.1ohms or less sense resistors. The power rating will depend on how many sense resistors are in parallel, how much margin you deem necessary above your maximum current.