Q: Are there certain benchmarks or guidelines you should be looking for to know if you're both communicating successfully?
Since EC is very personalized by each parent/child couple it is important to trust your intuition regarding your relationship. If you and your baby are in synch and "catching" any pees and poops in the potty (or whatever toileting place/receptacle you are using) you are probably communicating successfully. Even if you aren't "catching" anything at first, your communication is being received by the baby and at some point in the future you will likely start seeing a two-way communication.
There are both signals from the baby to the caregiver and signs that the caregiver can give the baby. Neither has to be present at the same time and both can build the communication. Sometimes a baby will not respond clearly to signs from the caregiver or not demonstrate understanding or interest in participating, but continuing to offer pottying opportunities and talking to the baby about his/her eliminations builds a stronger base for future communications and often leads to more potty use in the near future (could be hours, days, weeks, or months).
I, personally, think people should give it at least 3 months before deciding whether it works for them or not—there are challenges at all ages, but the older the baby, the longer it might take for the baby to start responding by using the toilet/potty even though the baby's communication skills may be more advanced; if the baby has been diaper-trained for many months already, he will need to be un-diaper-trained while learning pottying skills.
Q: What is the difference between communication and training?
A: With respect to toilet learning, I see that there are several differences. For one, toilet training has a very specific goal in mind—to get a diaper-trained child to use a potty or toilet instead of a diaper. It is usually viewed as an event that takes place at a particular point in time, usually involves some sort of method or technique and quite commonly, at least in our culture, involves rewards and bribes, possibly even punishments.
Communication—as practiced through elimination communication—does not focus on one end result, but focuses on building a relationship between parent or caregiver and baby. This relationship is based on trust and learning together, accepts a baby for his or her actual developmental stage (rather than what "should" be for a certain age), and allows the baby freedom in his or her own development. It is equally shared among parent (or caregiver) and baby, although at different stages of development one or the other will likely take more initiative than the other. It involves finding ways to work together in a variety of situations and both parties teach and learn from each other. The result of the baby becoming potty independent (and out of diapers if diapers or training pants are used in the learning process) is more of a "side benefit" than a goal. Patience is key and a respect for your child as a unique being is critical. Rewards and punishments are not used, and any pressure is counter productive (and not considered EC by definition). Sharing excitement with a child is wonderful (such as "Wow! You peed in the potty!) so long as there is no judgment passed (i.e. "you're a good girl because you peed in the potty!").