I have sent and received many items over the years via bus service. From legal documents, birthday and Christmas gifts, to electronics with never a problem. Very common too by the way. I would not rush to describe the items as computers, if asked, but would choose a more generic term such as office supplies, equpment, etc. I would prefer to use Metro as they always seem to be a cut above Caribe Tours to me.
If you say it is a laptop they will not take it. Just wrap it good and tell them it is something else. Metro is better for this than Caribe Tours. I have sent computers, laptops, and other office equipment with no problems with Metro.