What ports are you going to?
We did Venice to Dubrovnik and stopped at small islands and ports...such as Hvar,Koper,Piran,plus Split.
Spent 3 days in Dubrovnik,,,and still didnt see it all,,,we walked the city wall,,went to beach near there,,,saw all the tourist sites in Old Town...missed the funicular up hill(not opened yet). It was just fantastic,,but full of tourists during day...and quiet at nite.Try to get out of old town area and walk up hill to beach,,and great small seaside restaurants that not so crowded..Easy to do on own.
In general,,easy area to see on own and love just walking small ports and discovering ...unless you want to see some of countryside...the people that took shore excursions,,loved them,,but did not have time to see the port.So, a tradeoff.PS..everyone speaks some English.A spectacular cruise...water so blue and cliffs,beaches,SO pretty.