Vueling filght from Barcelona to Granada

Book it now if you are totally sure of your dates. I believe the fares often go up (cheaper rates sell out). Even if it drops a little, 39euros is still very good. Better to lock in that than risk an increase.

I agree with the above. Airline pricing is more sophisticated than just going up the nearer you get to departure. But upwards is the general trend. So it's not impossible you'll see the price drop a little if you check regularly for the next few weeks and get lucky. But an equal (more likely?) outcome is it will go up. And if you leave it too late, up by quite a lot given July is a busy time. Since you are travelling from north Spain all the way to south Spain, €40 doesn't seem very dear anyway.

Buy now -- but with two cautions. First, budget airlines sometimes change their schedules. Also: Run a dummy booking through the process to see what the inevitable extra fees might add up to. Bonus: Read the webpage carefully, especially regarding checked and carry-on luggage.

Thanks a lot for all of your suggestions!!!

This makes me to think about Renfe. Should we also book Renfe fare in advance (now) to avoid increase price for the ticket as well? Or Renfe fare is usually not change at all.
Thanks again!!

Renfre tickets tend to go up. I would for sure purchase longer train rides ahead when u can. Exception is a train trip that u are taking on your arrival to Europe when u can’t always be sure your plane will be on time. I had some difficulty booking Renfre online. Granted my Spanish is awful. If you have difficulty try Trainline or loco2. There are also short train rides that sell out like Toledo to Madrid and the reverse. Usually a day or so ahead is enough