Best advise above is prebooking. You have no chance to get in if there are no tickets left. I recommend looking early on the website and booking the towers is a good option also for looking on the work proceeding.
One way to go around when you like driving with e-bikes is ridemovi. It is bikes sharing, normally you will find bikes only a few 100m from the port. Take a look at the website. Not only in BCN but also in Rome, Venice...
In BCN its flat and there are good lanes for bikes, so you find your way through traffic easily