I did it last year. It was a draft fest because they had to cut the swimming because of 3 meter tall waves and with a 900m swim almost everyone left T1 together. The faster folks of the full distance caught the mid ones of the half. My only annoyance here is that Judges were not stopping and giving penalty cards to the people in the front, only middle and rear people. But the roads are very good and have good width, if the swim is done fully there should be enough space if you want to avoid drafting
Last year that week the weather was truly terrible, we had thunderstorms and a couple of days before Calella had streets drowning because of the rain. The first week of October in this area is always crazy and weather is super random. Im a local and I trained twice a week in that route ( Masnou to Calella and back ), did it so many times in the three months prior to the IM that I literally had every single Local legend in Strava and let me tell you something. I never, EVER in my life we had such strong wind. Its very common to have heavy winds that make sometimes going south or north hard and slow, but super fast and easy the other way around. But oh god that day. It was really hard going over 25km/h on one side even tucked into aero position, and I saw several people with disks almost crashing because of the gusts.
We had rain the day before and the same morning. Thanks to the volunteers that were helping us getting out of the water
https://www.youtube.com/...hannel=TheDarrenlast because it was hard getting out. In my case I was hit by waves several times until one of them lifted me and I ended up standing in the sand, so it was easy, but I had a friend that was there watching and the told me "I literally saw the same person coming out of the water 4 times"
Other than that, this year im doing the half in Platja d'aro instead, and I plan on repeating the full one in one year or two. Good luck and enjoy it!