Don’t I have a right to express my opinion without fear of being sued for libel or slander?
Yes, so long as your statement of opinion is just an opinion, and does not contain specific facts that can be proved untrue. For example, “The waiters and waitresses at Acme Restaurant are too slow and the food is too spicy.” This is a statement of opinion. “I got food poisoning at Acme Restaurant” is potentially a defamatory statement if, in fact, the restaurant can prove that you never contracted food poison.