Nick, my wife and I walked from Porto last April via the central route. Our first day of walking was April 7th. We enjoyed the route very much with the exception of the first day out of Porto. There are several long stretches where you walk on the shoulder of the busy N-306. Also a lot of cobble stones and the even worse granite setts as paving stones.
Knowing what I know now, I would recommend the coastal route out of Porto.
Once in Vila do Conde, you can cut back inland if you wish and rejoin the interior just before Arcos. Other than the first day, the interior route was really interesting and I would recommend it
As far as the month, April traditionally can be a wet month in this region, but we didn't have a single drop of rain in all the time we were in Portugal and Spain last year. This is unusual for sure and certainly not a guarantee of what to expect.
Keep in mind April will be much less busy than June. We had absolutely no issue with accommodations last April. In June you are in Camino prime time, so reservations for stops are probably a good idea.
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