In addition to other places we've already found, just came across 2 possible additional trips we might be interested in taking for a day trip ....Xativa (south of us) and Segundo (north). Anyone been to either one and could offer thoughts? Would train or car be better?
I haven't been to either town, so I don't know anything about the roads, scenery, parking, etc., but I see that Xativa is less than 45 minutes away by train from Estacio del Nord.
Sagunto is 27 to 35 minutes away by train. Sometrains depart from Joaquin Sorolla station. It takes just about 10 minutes longer to use a regional train from Estacio del Nord. The fare difference will not be large in absolute terms in most cases, but if you buy on the day of travel, do look at all the options. The Promo fare on the Talgo (which can sell out) is 8.50 euros one-way, so the full fare must be over 10 euros. The regionals cost 3.80 or 4.15 euros.
Edited to add: I found some brief comments about those towns in the research document I prepared for my 2019 trip to Spain. Included for what they are worth:
Sagunto: Walled Roman seaport, no longer on the coast. Old Jewish quarter with extremely narrow, steep, twisting streets.
Jativa (Xativa): Market on Tuesday and Friday (2006 source--verify!). Markets are usually morning only.