I say I love you, irrespective of the place, whenever I am inspired to say it. I also believe we benefit from saying it - that it enriches you/your life and it expands one's capacity to love.
I say it to people I love daily becasue it's important to me that they hear it daily, that they know it's true, without any doubt.
However, I would draw a distinction too between saying I love to people I'm firmly ensconced in a solid relationship with and saying I love you for the first time to someone in a new relationship.
What am I afraid of? I don't know that it's fear, as much as a heartfelt concern for the comfort of a new SO - that it's more about a solid progression of a new relationship, simply because we are building something.
Even though the foundation is built on essentially on love, I believe knowing for certain is what matters intially, over saying it or hearing it.