Both sex and death are prominent in the play.
These young people live in a world of violence and like any teenagers, they think about sex, they talk and make jokes about sex, in other words, they are normal.
Mercutio is perhaps the most obvious for his sexual talk and humor.
Tybalt represent the violence. He must push issues to show his manliness because in his world that is what men do, they fight each other.
It must also be remembered that sexual union was thought to be a small death, so yes, the ideas are related.
Romeo and Juliet both choose physical death over the world of violence in which they live.
OK, the quote. All Romeo is saying is that he will send his servant to give her a rope ladder so Juliet can lower it for him to climb up that night.
When you consider that Romeo and Juliet fall for one another - largely due to a sexual (or physical) attraction, and then that the long standing fued between their families has been resulting in hatred and violence for many many years, you could conclude with this statement: Because what started as a physical attraction lead to marriage, Romeo and Juliet were destined to die.
Think about the order of events in the story. Romeo goes to the Capulet party (knowing fully that he is not invited) to get over his attraction to Rosaline. He falls immediately for the beautiful Juliet. They rush into a very immature relationship. They get married quickly in part, because in those days, sex was out of the question before marriage. On the very day Romeo is excited to spend his first night with his new wife - his genuinely pleasant attitude angers his now cousin-in-law, Tybalt, provoking him to a fight. Mercutio dies. Tybalt dies. Romeo is banished (a fate just as bad as death). And through a series of slightly more complicated events, both Juliet and Romeo die - all because of Romeo and Juliet's physical desire for one another.
If the two had waited to cultivate a more mature love for one another - one that went beyond just the physical attraction (one that undoubtedly takes more time), we can assume a few things would have happened differently. Certainly they would have been more level-headed in decision making. Likely they would have eventually included their parents/families in the relationship, rather than keeping it a secret. Hopefully this would have brought the two families together before a hasty wedding, and therefore prevented the violence and death.
I think a major lesson to be learned here (that isn't so far from reality) is that "new love" based very highly on a physical attraction can lead to hasty and immature decision making - which can be very destructive.