I am a local from malta - if you want you have a shuttle bus service to valletta just outside the port at a minimal charge. so, you can avoid the walk too. valletta is worth visiting - do not miss st. john's cathedral and upper barrakka. by the way, locals speak english well and will help you for sure. if you need something to ask before your cruise, just ask and i will try my best to answer you before your cruise. avoid cabby rides....expensive!!! have a nice holiday and enjoy your visit especially in malta. it is good weather at the moment in malta.
Re your question on the distance to the town in malta. it is not that far but it is avery steep walk and you should be aware that it envolves a lot of steps . i was 67 when i did it and it was a struggle but worth it .
We caught the local service bus at the dockside, drops you right in the centre of Valletta, great place, plenty to see and do, shops also good, very pleasant downhill with some steps back to ship or again catch the bus. enjoy, we did.