Why wouldn't his visit to Sophy be as much of a duty call as his visit to Edwards? Seems like he intended to do both, and vistied Sophy first because it was closer. If he's just come ashore, Somersetshire is much closer to the coast than Shropshire (where Edward is) - he'd have to go through Somersetshire to get there, in fact. (Love the Persuasion Gazetteer! ;-)

I agree that once he was at Kellynch/Uppercross, that he made excuses to not continue his journey. Hard to blame him - he is universally admired and made much of, he has the attentions of lovely young ladies and good hunting, and he in genuinely fond of his sister and brother-in-law. He is having too good a time to move on and, as his time is his own now, why not tarry?