I think that depends on what you are doing, how many people you have coming, and where you will be protesting. I would check with your local officials to find out the correct answer for your area.
I've organized dozens of protests of various sizes and complexities here in Florida.
Not once have I secured a permit. Not once have I needed one!
That being said, here is my "experienced" take on permits. If you want to do a parade in a street, you will need a permit. If you want to do a protest on a sidewalk or grassy strip next to a public road, you probably will NOT need a permit.
You have a constitutional right to protest on a public sidewalk. Never forget that. Obviously, if you secure the permission from a private sidewalk, you can protest there also.
Re: asking permission. If you must, don't go directly to Town Hall and say, "Do I need a permit to do so and so?" This will guarantee that they will say YES. That's their job.
Make discrete inquires to a local cop or someone in a local Republican party. Someone has some experience. Going to City/Town Hall or police station almost invaribly will make things more difficult.
If you are planning to do something to surprise the opposition, asking for a permit is the best way to alert the opposition to your plans!
I used to send press releases out in advance of what we were planning to do. I do not do that automatically any more as those pressitutes always faxed or called the opposition as to our plans.
Think long and hard about permits.
My advice: Avoid them if it is legal to do so. In the overwhelming majority of situations and locales, you really don't need them, IMHO.