Is there anyone that have been walking fram middle of april til middle of may, and know how the weather is like? Im not sure what clothes to bring...
And; should I reserve space at the albergues?
I am walking in the middle of April as well, and my first time. I have done a lot of research on the topic, and at that time, you need to be prepared for marvelous weather. The first week will be cool and variable with +5C mornings, and +15C afternoons. Just kidding, nobody knows what the weather will be!
Be prepared for rain. Walk with your rain gear, in the rain, and get used to it.
Be prepared for possibly walking in +5C temperatures. Layering is the key. I found that a wool short sleeve base layer, a polyester pullover, and a light fleece jacket worn together is good down to 0C. If its windy, I add the rain gear (jacket or poncho) to block the wind. As it warms up, off comes the fleece, and then the long sleeve pullover. Do not take anything cotton....its heavy and takes too long to dry. Stick with merino wool and polyester. Take at least three pairs of wool socks. Take a change of shoes (like sandals) for evening. Take a hat to keep both rain and sun off your face. I have a pair of shorts, and a pair of hiking pants that are very light.
Later in May, I expect some days at +25C, which is shorts 'n T-Shirts weather. Your pullover and your fleece should be very light. You're going to need them, but you're also going to carry them a lot, and weight is important.
You should also decide what you are taking, and walk with all of it both on your back and in your pack, to get used to your clothes before you go, and so you get used to the weight of the pack.
As for the albergues, I booked the first two days of the trip, and after that, its going to be come-by-chance. Maybe I will regret that decision, but the forum pros here think not. See you on the trail!