You are most likely to meet people for climbing in Rodellar, Ceuse Frankenjura and maybe Margalef. Rodellar will be getting warm in June though the Spanish climb all summer, seepage should not really be a problem, but it is different every year depending on weather in winter / spring - check before you go. Good place to stay in Rodellar and meet people is Kalandraka Refugio. Ceuse and Frankenjura might be your best bet in summer without a car, though Frankenjura can be hot and humid and you will rely on meeting people for transport. Gorge du Tarn is baking hot in summer best avoided for climbing during that time. Margalef is best in spring and autumn and winter is ok too, and you are likely to meet climbers if you stay in the Refugio. Just pick a starting point - like Rodellar and you are most likely to meet other climbers who might have a car and go other places and take things from there...