For the most part no. If you have a location that is amenable to have a gathering you do not need to get permission for the group to demonstrate. The ACLU has a great summary of how free speech and the right to assemble work in the USA.
However if you want to do so in a public space then you may (and most likely do) need a permit from the local (Usually city or county) government to use that public space for your demonstration. In general speech is protected so the permit issuer must have a very compelling reason to deny a group a permit. That the agency does not want your group demonstrating is not enough to deny the permit with a very few exception like those groups that have been found to be criminal organizations through the RICO act, or your group has a standing injunction from the courts that prevents them from demonstrating in the jurisdiction.
The occupy Blog put it this way:
Yes, generally you cannot protest outside of a person's house. (This
can be different for a public official. Keep in mind that if the
house is located in a residential area, there can be strict limits on
noise, parking, etc. ) There may be limits on protesting outside of
someone's place of business. Harassment is not a protected form of
speech, so it depends on what your protest is about and why you would
be in front of someone's house. Also, many locations limit or
prohibit protesting outside a medical facility. Many publicly-owned
schools, especially grammar and high schools, do not allow protesters
on the property. There may be limits in parks; most cities require a
permit to hold a protest in a park if the group has more than a given
number of participants. Common numbers are 25 or 50. Check the
municipal law. Most parks contain protest activity to certain
locations. Most parks also limit or prohibit the use of sound
amplifying devices, such as amplifiers or megaphones. You need to
check the local laws and the rules regulating a place. If you plan to
hold a protest in such a place, you would be wise to consult with a
lawyer first.