Hi Annie,
I walked May/June this year Porto-Santiago and found the route absolutely beautiful. I didn't have any fears about walking alone (though I only walked some of Spain alone my boyfriend having given up after walking through Purrino but my friend walked some of the portugese section alone a few weeks previously without any problems). I have to say though unlike Claudine (above) I only met one other woman walking alone the whole trip (a Spanish lady) and without exception everyone I met expressed extreme surprise at my being alone... I have never encountered any problems walking the camino path in the daytime alone - everyone I met on this trip was lovely - possibly the locals are less jaded by pilgrims than on the Frances and everyone I passed/talked to was very, very friendly and helpful!
I'd be lying if I didn't say I had a couple of uncomfortable moments but crucially these were in the evenings when I was out of pilgrim gear and just looking like a foreign woman walking around alone (my hair gets a bit blonde in the sunshine!) it was mainly in the bigger towns, in the rural areas everyone was very respectful! I was grabbed by a guy in Valenca but he went away when it was clear I couldn't understand what he was saying (making me suspect he just wanted money). I'm not saying this to put you off I'm just being honest. I would walk it again the whole way alone in a heartbeat so don't even worry about it just keep your wits about you as you would in any country!
I would say I found the Portugese part (once past Porto) some of the most beautiful walking. The only difficult part was the long stretch from Barcelos to Ponte De Lima where there is virtually no accomodation. I believe there is a possibility of somewhere before Ponte De Lima but I understood from some other pilgrims that it was closed when they got there. The centres of Barcelos and Ponte De Lima were both lovely. There was a medieval festival in Ponte De Lima just a few days after we we stayed - maybe check next years dates? - it might be nice for you to arrive in time to catch that/skip it depending on your taste! Ponte De Lima is a lovely place for a day off - we had one to recover from the previous day's long walk and I really enjoyed it.
I found May quite busy with pilgrims (though nothing like the Frances!) and there was never a shortage of beds, you can take your time stroll and stop without worrying about sleeping arrangements. Once it turned june though the number or people staying the in the albergues went from about 20-50 down to about 6!!!
The worst stretch of the trip was about 8km thorugh industrial Purrino, it was absoutely awful the worst bit of camino i've ever seen i think! Made much worse in that it was pouring with rain that whole day with the trucks passing drenching us in backspray - maybe in sunshine the constant trucks thundering past factories might have been more amusing.... If you the kind of person that skips the awful bits then take a taxi though that stretch....
If you can't make it to Redondela it might be worth stopping Mos, I understand this is a very nice albergue and the locals there were amazing! We asked if there was somewhere to get coffee and they took us into a private reunion party they were having and made sure the barman got us drinks!!!
If you have lots of time you could always walk back to Porto to catch your flight!?! The route is very well signed backward - particularly in Portugal where I think it is a pilgrimage route in itself down to Fatima?
Have a lovely time!! I'm sure you will enjoy it!