The hand shape that creates the sign I LOVE YOU is rather complex - it combines the signs for the letters I, L, and Y. My family didn't let that stop us from incorporating it early on into each of our sons' signing repertoires, though!
It was important to us that they be able to participate in the exchange of this sentiment that is used in our family. We knew that they would show us their own versions of the sign, based on the research done by the Signing Smart founders, so we didn't hold back. We tell our boys multiple times a day that we love them, so we just added the sign. For us, this was a sign we both knew long before we had kids, so combing the two wasn't a big deal.
I tend to add a little hand wave when I sign I LOVE YOU. My husband picked up on this somewhere along the line as well, so this is the way our boys saw this sign. Sure enough, after some time, we started to see that hand wave come back to us!
At first we saw the wave of a loosely closed fist.
Then it turned into a pointer finger. Around the same time, we started to hear verbal attempts as well. Seeing little hands wave and hearing "a-you-you" during drop off time at day care definitely made the moment a little bit sweeter and easier to survive!
After much "practice" (I say practice with quotations, because there was never a time where we drilled our boys or forced them to show us a sign - we always used the 4 Keys to Signing Smart Success. Their practice was done in choosing to repeat the sign.) and some muscle development we now see our older son sign I LOVE YOU clear as day! This is no short process. We started to see his hands work toward the correct handshape around age 3. At first he had to help his fingers get into the correct positions as the muscles learned to do something new. Now, at 4 he can sign this without even thinking twice about it!