Plants will indeed consume almost any form of soluble nitrogen. When I used to go high tech with my plants, I intentionally added nitrates as fertilizers. On the other hand, the plants will not interfere with developing a nice robust bacterial colony in your filter, they might make it a bit harder to interpret your test results though. If you decide to cycle with plants present, be sure to mention it when you ask what your chemistry means so that we can take their presence into account.
The platns won't affect the tests, they will affect what happens to the ammonia you are introducing by absorbing some as fertilizer.