1. There was indeed an Eduardo San Juan who worked for Boeing at the time when the LRV was being developed. He wasn't a senior developer, just one of the technicians.
2. The inventor of the LRV are the following men: Dr. M.G. Bekker, Bruce Velasco, Frank Pavlics, Sam Romano. Thus, San Juan had NO HAND in its design concepts and development. He probably worked on it like other engineers at Boeing, and that's the extent of his contributions.
Note: There was indeed an Engineer named Eduardo San Juan, but he worked on a project called MoLab (Mobile Laboratory) Rover, a subproject in the Apollo programme that aimed to land a large pressurized mobile laboratory on the moon. San Juan did a study and even made a few sketches of his large rover design, but it is important to note that he did all this TWO YEARS after Grumman already got the contract to build the smaller LRV, which was the final rover design that got onboard Apollo 15, 16 and 17.
Note: Now this is a good article that will "put the nail in the lid" of this urban legend. READ HERE.