60d, 17-55 and 35 1.4L enough for travel?

believe me, I own and love the 35L (see my username...) but you really don't need it in parallel with the 17-55. The 70-300 is an amazing lens, you must take it if you like to shoot tele, which I think you do, otherwise you wouldn't own it.

My advice is based on my long experience with the 17-55, 35L and the 70-300L.
On my last vacation on europe I took 5D II + 17-40L, 35L, 70-300L and 135L.

Everytime I left the hotel I took two lenses with me. At night I took the primes, during the day I took the zooms.

If the 17-40 had 2.8 and IS like the 17-55 has, I think I would have left the 35L at home.