Just tell them you've made other plans for that time period? Or explain your living & dog situation, and ask to be taken off the list?
Actually, if you do show up, you can get out of it fairly easily. If the case is about a burglary, the defense lawyers will often ask if any of the prospective jurors have ever been burglarized, so raise your hand. If it's about child/domestic abuse, they ask if anyone there has been abused, or knows anyone who has been physically/sexually abused (raise your hand). Whatever they ask, tell them it has happened to you or to someone close to you (be opinionated) -- they prefer impartial jurors, not sympathetic ones.
Sometimes, you have to show up at 8 a.m., they quiz the prospective jurors, pick the ones they want and the rest are released. BUT sometimes, they're getting set up for several different trials, so they either send the 'leftovers' to another room, or tell them to wait in the same room, and then another group of lawyers will come in and sift through them. There is often a gap between the quizzing, so you might ask if you could run out for a few minutes to walk the dogs.
Be sure to take a baggie -- you don't want a ticket for soiling the delicate grounds of the county courthouse.