I often go to penghu for work (windturbines).
I see 2 problems:
1 - you might have some problems for renting stuff in november or march as it is the low touristic season
2 - You need to speak chinese, not so many peolpe in penghu speak english.
Here is the link for the surf club located in Shanshui beach http://tw.myblog.yahoo.com/penghusurfclub/
And an other website in english about penghu http://vitalpenghu.wordpress.com/
I just moved from Canada to Niseko Hokkaido Japan - have decided Penghu will be my new go to spot.
Looking for accommodations in Penghu near Longmans Beach preferred or other wave windsurfing spot - for 1 person for 45 days mid October thru November 2012, also 45 days March to mid April 2013. Note also looking to rent good wave gear - prefer JP & NP.