It is Juliet who says the above lines in Act II, Scene V. In the preceding famous balcony scene, she and Romeo have already made promises to marry, and now in this scene, Juliet is speaking these lines while waiting for Nurse to return with news from Romeo about their wedding plans. Juliet is feeling very impatient to learn her news and feels that Nurse is returning far too slowly because, as Juliet says, "[S]he is lame," meaning that Nurse has some sort of physical handicap that makes her move slowly, possibly obesity. Feeling frustrated that she has to wait on Nurse to learn if Romeo really plans to marry her, Juliet comments that "Love's heralds should be thoughts" (II.v.4). Here, "heralds" refers to messengers, and what she means is that the messengers of love should just be thoughts. Lovers should merely be able to communicate with one another simply by thinking of the other. The reason she wishes she could communicate with Romeo through thoughts alone is that thoughts travel "ten times faster" than any other messenger, such as her nurse. Juliet even continues to poetically say that thoughts are even faster than sunbeams that chase away shadows from hills being darkened by clouds, as we see in the lines, "...Which ten times faster glide than the sun's beams / Driving back shadows over low'ring hills" (5-6). The verb lowering(it) can be translated to mean darkening, or threatening to get darker due to the weather; hence, we see that in the last two lines, Juliet is comparing the speed of thoughts to the speed of sunbeams (Random House Dictionary). Therefore, what Juliet is ultimately saying in these lines is that she wishes she could learn Romeo's news much faster.