Unless you are unlucky and are caught, physically in the middle of a strike/protest that turns violent, local strikes rarely tourists. Often, they also don't affect all the locals. In the U.S most protests and strikes are peaceful. MAsses yelling and screaming scares Americans as they are not used to it. There have not been violent protests in the U.S. since the end of Vietnam war.

In some countries, protesters go on a rampage, setting shops, buses and cars ablaze. Typically, strikes target the Government and its operations, such as offices, public transport, or airlines. I doubt you will see protesters congregating at places frequented only by tourists. If you stay away from areas where an active demonstration is going on, you have no cause to be worried.

Some of those demonstrations do look scary. I saw one where striking students stopped a city bus, asked every one to get off, toppled the bus and set it ablaze. I saw a mob of students pushing on the bus rocking it back and forth until it toppled.