Why do Spanish speakers speak so fast?
I am an American who has travel to South America, grew up around Spanish native speakers and now live in Europe. If you are asking if Spanish speakers speak fast, the answer is a qualified yes.
When you are learning any new language, it always seems native speakers speak fast. My friend has studied English her whole life. In fact she is a teacher of English for foreigners. However, when my other friend (from the States) and I are together talking English, this teacher she says often she only understands the words, but not the meaning as it is too fast and too idiomatic. My conclusion is a language is at an apparent rate of speed because we are not use to it.
Therefore, to all language learners hearing native speakers whether they are Hispanic speakers speaking fast or English speakers.
Why Hispanic speakers seem like they talk faster
I think the Spanish language is very staccato and musical. Staccato is a form of musical articulation that can sound very forceful. This makes Spanish seem quick and even accelerated. Further, I think Spanish being a romantic language, has a lot of passionate speakers, that you might not find with say, Danish speakers. Therefore, Spanish seems quick when there is emotion connected to it.
Latina language speakers are hot blooded, whether they are from South American Spanish from say Peru or European Spanish like in Madrid or Barcelona, Spain. I know this is a stereotype, but Latins have an emotional culture.
People who are asking the question do Spanish people talk fast, often remember a TV show like I love Lucy with Ricky Ricardo or some moment when a Spanish women in a shop got upset and was yelling in Spanish. This conjured up in their mind images of people from Latin countries all over the world behaving like this in normal circumstances. People like to look at the exception than the rule. This is why I think that people have this impression that Spanish is about speed talking. However, this might not always be true, it might just be perception.
On the other hand, in warm countries people tend to take it easy and everything can be done mañana. Therefore, you can argue the contrary. Below is an example of a quick and slow talker.
I knew this one Spanish girl from the gym who had a very soothing voice and talked in a melodic way. I would not say she talked fast. Yet, on the other hand her friend from Puerto Rico talked a mile a minute. Both Hispanic speakers and one faster than the other.
If you were to evaluate the actual word rate I think you would find that Spanish speakers speak about eight percent faster than English speakers on average, but it depends on the region and dialect. You would have to do a word count and compare it with other languages in a large enough sample. This is the only real way to tell when you strip away all the emotions and stereotypes that cloud our imagination. Above is just my guesstimate. I am very curious what you think about this, as I am not a native speaker.