Does using lemon juice instead of lime juice make a difference when making guacamole?

not really. you can usually use lemon instead of lime

You are only adding the citrus to keep the avocado from going brown. If you add so much that you can taste it, you have added too much. It is like peeling an apple and you can watch the meat of the apple turn brown, so goes it with avocado. Put a little citric acid on the apple, and it will retain its color. Put in on a peeled avocado and it keeps that pretty green. You are not trying to flavor the dish, you are trying to maintain the attractive color.

not really a difference, but limes have a stronger memorable taste

it is personal preference to which you use! and do you know that it also makes no difference whether you use bottled juice or fresh squeezed!