We were fairly lucky!
We were here in June, arriving at the car park before it was open.
This was an excellent time to come. NO crowds of people, we could walk up and buy our admission ticket without queueing, we had the pathways alone or with less than a dozen people for the good part of the day.
It only became busy, when I reached nearer the second entrance as this was later in the day, and tour guides and groups were here by then.
This made the park a much more beautiful experience, and much better for photos too!
If you have time spending a weekend or a few days in this place of tranquility and natural beauty is of course a great idea. Lika region is mountainous region and this can be a great escape from the summer heat as well.
Fondest memory: But I must say I do not agree with those that insist that staying here overnight is a must. In my opinion a daytrip to Plitvice is sufficient enough if you are just visiting Croatia for a week or so.
Park is conveniently located approximately halfway from Zagreb and from the coast (on the D1 road and NOT on the A1 highway!) making it easy to do it as a daytrip whether you are returning on your point of departure or simply stopping on Plitvice on your way to/from the coast.
If you take, say, and early morning bus from Zagreb (let's say the one at 8), you are on Plitvice at 10.30. Count 7 hours for the longest route and a 1-hour lunch break and you can wait for your bus at 5.30 pm and be back in Zagreb by 8pm (or in Split approximately an hour later).