We were staying for 30 days in September with a 6 months old and overall we had a great time. On the plus side Gladys provided some extras for our baby such as sitting chair and a bath, which was very nice. The beach is only a few minute walk away and we could come and go as we wanted. The area is generally quiet and nice, though I would recommend staying on Cabanyal side as it has a nicer vibe than Malva-rosa. The transport links are excellent, we had no issue getting to old town and airport with the baby.
On the other side, the place is 3d floor, which Gladys kindly informed us about at the booking stage. We decided that we'd still book and bring the baby stroller up and down the stairs. It turned out that the communal lobby is rather spacious and protected, so we ended up leaving it downstairs during the day and took the top part upstairs at night and folded the wheel part downstairs for the night. There was another couple with a baby in the building and they did the same. We had no issues with neighbours on this, hopefully Gladys didn't receive any complaints either.
It is worth mentioning that there are 3 houses in the 50 meter radius that are going through renovation. It may get noisy during the day, which was sometimes an issue for us as the baby needed 3 day naps. That said it wasn't aways a problem, only occasionally. The nights were very quiet. If you are adults only, you would have no problem with it and if you are considering staying with the baby, please talk to the host, so she can update you on the latest development.
Otherwise, please read other reviews, they cover all aspects of the flat really well.
Have a great stay!