I looked on the Naruto Filler list (http://www.animefillerlist.com/shows/naruto, this is the one I used for anyone asking) and it says that after episode 135 all the episodes just become filler. I was wondering to save myself a lot of time, could I just start watching Naruto Shippuden after ep 135
The short answer is - yes. You can start watching Naruto Shippuden after watching episode 135 of Naruto without any harm to the overall Naruto storyline understanding.
Yes, You can. After Naruto episode 135 they are all fillers. However fillers are interesting to watch but Shippuden is better than the fillers. After episode 135 you can jump straight to Shippuden without missing any of the main storyline. Also, as "Ch.Siva Ram Kishore" has added... There are zero references to the fillers from Naruto in Naruto Shippuden. Overall there are 220 episodes in Naruto and you only need to watch the first 135. The final 85 are all fillers and you can just Jump straight to Shippuden and save tons of time. SO YES.
(!! SKIP THE FILLERS AND GO STRAIGHT TO SHIPPUDEN !!)