I don’t think any of us at Pololu have worked with fuzzy control systems, so we probably can’t offer you any particularly useful advice. It would probably be up to you to determine whether the fuzzy control algorithm(s) you want to use could be ported to the microcontroller you want to use.
Please note that the m3pi consists of a 3pi base with an expansion board on top that is intended for an mbed to plug into. The mbed is usually programmed in C++ via its online IDE.
If you are trying to find an appropriate sensor, some of the Sharp distance sensors or sonar range finders might work for you. We have an example project that demonstrates how to use the Sharp analog distance sensors with the 3pi, and this thread discusses using them with the m3pi. Beyond that, however, it is largely up to you to determine what you will need for your project, although we can answer any specific questions you have about particular products.
Just in case, I recently developed a simple Fuzzy Controller for line following on 3pi using EFLL Library (zerokol.com/post/51e9324ee84c55a1f5000007/1/en) . So in conclusion the 3pi es fully capable to run Fuzzy code without further modification as far what you only need is line following. If more sensors are needed like distance sensors or encoders probably the m3pi should be a good choice.