The boardwalks dangerous. No , hmm, but you have to pay attention to some aspects.
A) next to pedestrians the boardwalks are used by bikers and specially you have to take care for them coming from behind. you will hardly hear them and all of a sudden they will be next to you. Shocking experience If you are in your walking flow or using your headphones.
Specially during weekends and holidays there are lots of bikers,also in groups ,using the boardwalks.
B) a tip for your tip. If you use poles and walking on the boardwalks ,take off the rubber tips . the planks of the boardwalks sometimes have big gaps in between so you can loose your tips. Trying to get them back underneath -sometimes there is more than a yard underneath the boardwalk where is the sand, plants , dirt etc
-you will hardly find them back , if you are able to come underneath the boardwalk anyway.
Avoiding the boardwalk ,you could consider to take the metro out of Porto, direction Póvoa de Varzim and go out at Vila do Conde . You will then directly on the way to São Pedro de Rates on the Central caminho at the end of the platform of the metrostop -in the direction where the train was coming from you'll see a river. Keep the river at your right and you are on the waymarked route of the caminho Central
The metro to Póvoa de Varzim is not the same that comes in Matosinhos .
To walk to Matosinhos out of Porto along the Douro river and the Atlantic ocean is great. You could walk to the Leixões bridge over the Porto harbour and the metrostop Mercado. Then you will have a great time walking . Take the metro from Mercado in the direction of Porto to the stop Senhora da Hora and change there for the metro to Póvoa de Varzim to Vila do Conde for the Central caminho or the Coastal or go on to Póvoa de Varzim and continue the coastal caminho there. To avoid the wooden boardwalks
What you will miss is the nice camping to stay the night in Angeiras.
As our famous Dutch scoccerplayer Johan Cruyff said " every advantage has a desadvantage "
Pega bem e bom caminho