Pisa is very compact. It should  present no problems of navigation. A 2.50euro foldout guide is more than adequate. The airport is a 10 min. bus ride or 6 min. on the train. In fact foot is both the quickest and most practical mode.Disable or infirm visitors will find taxis dedicated to their needs; consult the airport web site.

If you are driving be aware that you can get a fine of 121Euro if you drive into a restricted traffic zone. Fair enough but the problem is that signage on the  turns into the zone (which can be nose to tail with traffic) is in some places practically non-existent. If you are driving into to Pisa (and this includes not just the city centre) think very carefully about whether or not you want to risk a fine - best option would be to try to get a map of the restricted zones before you go.