Flew out of Taipei around noon in mid-December one year and it was in the low 70's. Biggest problem is the congestion, busy streets, lots of people, dog cr*p, etc. I would suggest finding a track near a university to begin with and then try to find other places to run as time goes on. Pretty much the same comments that you'll find here:
http://www.runtheplanet.com/location.php?q=2&l=1248
Could be worse. You could be stuck in Kaohsiung at the bottom of the island. The pollution is a lot worse there than in either Taipei or Taichung. Maybe you can dig up something useful regarding terrain, weather, parks, etc. here:
http://en.wikipedia.org/wiki/Geography_of_Taiwan
One thing that you'll find interesting is the food. You'll get to try Smelly Tofu Soup, Pork Blood Soup, and lots of other fun stuff. In France, food is everything. In Taiwan, everything is food!