We have just returned from a cruise on the Sea Princess which included a stop at La Guaira, we did an organised trip which was the grand tour of Caracas including lunch it went to old colonial house turned into a museum a cable car ride (which was very good) and a visit to a glass factory also not bad but the house visit was a waste of time not very good at all. There was quite a few trips that just did the cable car and factory. Do not attempt to do a trip on your own, down town La Guaira is awful the poverty is unbelievable and Caracas also. Hope this is of some help to you,.
We usually do our own thing, but following advise from this web site we went on an organised trip from the ship when we went on the same cruise in November. We went on the jeep adventure which we thoroughly enjoyed! You can get stunning views of Caracas from the cable car if you are fortunate enough to have a clear day. Most other passengers that we spoke to stayed on the ship or went on an organised tour from the ship. As Smith has said I wouldn't recommend doing a trip on your own. Have a great time whatever you decide to do.