What water temperature do you wear a wetsuit?

...and I feel the time saved on the swim will offset the additional time in transition to remove the wetsuit.

I did a tri earlier this year with a ~400M swim and less than half a dozen of the 150 participants wore wetsuits.

on a swim that short I'd prolly agree. I was thinking traditional sprint , 80O yds and longer. At those distances the time I save is greater than the time I lose in transition and  the energy I save during the swim is the larger benefit anyway.

to the OP... it does not matter how many of the people in your tri wear, or are planning to wear, wetsuits.  That is irrelevant to your question.

For my first race, it was a 400m swim, in an outdoor pool, and probably about 5% of the people wore wetsuits, myself included.

Why did I wear one? Because I am a poor swimmer. It takes me about 30 seconds to get the wetsuit off, and it saves me about 15 seconds per 100 yards.  So I gained around 40 seconds with it, and it helped me mentally as well.

For some people, it's not worth it because like bear says, it's a wash, time-wise. But maybe that applies to you, and maybe it doesn't. This site is called beginnertriathlete.com, isn't it?