Our first two cruises were in November. Had never heard of sea lice back then and never took precautions. No problems at all. Also, never took bug spray with us. However, our sunscreen is the Avon SSS with bug guard.
We just finished our first summer cruise on 8/28. Again, debated about getting SafeSea -- decided not to spend the money. When we went into CC, it was loaded with floating urchins! We just avoided them and splashed them out of our way. We never had any effects from any bites or irritation from anything in the water. We brought bug spray for the Mexican ports, but never used it at CC. Again, no problems -- didn't need it.
For November, I wouldn't bother with either bug spray or SafeSea, but that's my personal opinion.