Your rights

Owners of private property can determine what speech is allowed on their property. Protesting in public areas such as streets, sidewalks, and parks is the safest option.
While on public property, you may photograph “anything in plain view”, including police and federal property.
Permits are not required to protest, given that you are not obstructing traffic. If obstructing traffic, police may move you to sidewalks to let others pass.

Rights of Police to disperse protests

Police may not disperse protestors unless there is “clear and present danger of riot”, disorders, interference with traffic, and threats to public safety.
Police may enforce curfews imposed by localy jurisdictions.
Police must issue clear and detailed notice of dispersal orders, and allow for sufficient time to vacate the area.

“The purpose of legal observers is to monitor, record, and report on any unlawful or improper behaviour.”
Anyone may request an ACLU legal observer to monitor a protest. ACLU legal observers are neutral protest attendees who will record their observations during a protest. They will be wearing a clearly visible blue “ACLU Legal Observer” vest to identify themselves.
Legal observers for Texas can be found here, and observers for other states can be found by searching “ACLU legal observer request [state]”