I would put the plants in now also. I would set everything up, including plants and lights, before you put the fish in.
The "good" bacteria that cycles a tank will still colonize in a planted tank once the fish are added. You'll still need to test for ammonia and nitrite levels, although they may be less than a tank that is cycling without plants. The plants will absorb some of the excess ammonia products, so your test kit may show a lower result than expected if you were to cycle without plants.
For the plants to completely absorb the byproducts of the nitrogen cycle right away, I think it would have to be a moderately to heavily planted, high-light tank to drive the photosynthesis. A few crypts in a 1.5
wpg lighting, for example, won't drive the photosynthesis enough to completely absorb the nitrogen compounds put off by the fish.
I have started small tanks from scratch with plants, fish, and medium light, and I have gotten an ammonia reading of .25
ppm. I did small water changes, just as you would do with a tank cycling without plants. Within about four days (the length of time will probably be dependent on your bioload) I got an ammonia reading of 0. I didn't get a nitrite reading, or else it's possible that the nitrite was only in the tank very briefly and I missed it during my testing. My nitrates were always 0, and I have to dose for them. Since I never got a nitrate reading to signal that the cycle was finished, I kept testing ammonia and nitrite for an additional week just to be sure that they were 0.
Hope this helps a bit!