Which is it??
Yes, I suppose that was a little contradictory.
By "non-rushed" I was mainly referring to the act of actually getting to the site (would there be annoying traffic jams at all hours of the day that would make me nervous about making it back on time?, etc.) But your comment about 30 minutes (45 with plane) sounds good, so depending on how long it would take me to get from the port to La Linea, it sounds like it should be possible to make a visit.
In this case, I would consider a "reasonable" visit to be one where I could see everything that I would be "allowed" to see, even if that were somewhat underwhelming. I am not as particular as some community members when it comes to really drilling down into a certain sites ouv, if it is not straightforward to do so.
The Mediterranean Steps would be something I would normally be up for, time permitting, but in this case some circumstances might cause me to skip that. I'll have to play that by ear and will need to make final decisions for all of this at the last minute, anyway.
Thanks for your comments!