RJ,
I have owned an '05 P150 for almost 2 years now and I love it. Has been very reliable and runs like a champ. Will try to answer some of your questions.
Will People 150, in a comfortable fashion, make it up Federal Highway (US-1) ninety miles, from Fort Lauderdale to Port St. Lucy? Yes, it will make it, but not in a comfortable fashion. It's great for around town and short jaunts on the highway, but 90 miles is definitely pushing it.
You might think this question is stupid, but, I have seen some owner's manuals for scooters written in almost unreadable English. Does the People 150 come with an owner's manual that is well written in English? Understandable....yes. Well written....no. Has some contradictions and errors.
How easy is the scooter to maintain and repair after the warranty is up? Relatively easy.
Is there a maintenance and repair manual available for it? Yes.
How much has the design changed? Not sure, but I believe the newer models are identical to mine.
What are the major pros and cons of the People 150? Pros...Great bike for the money, reliable, economical, handles well and is fun to ride. Cons...about the only thing I can think of is it sometimes takes a while to get parts.
In summary, I think it is a great little scooter, but probably a little too small for how you plan to use it. You might consider the Yager. Good luck!