Our ability to translate the language will greatly hinge on context.
From your question, it seems you are describing a singular text. Possibly a collection of news articles or even a "welcome to the planet" type guide. If we were to find this isolated from anything indicating its origin and purpose, we would have almost no hope of translating it. (An infinitely powerful computer would be able to generate many possible translations. It may even be able to calculate the most likely one, but we could never be sure.)
If, however, this was not a singular text, but rather the sum of text found about the ruins of a city, we could certainly translate at least most of it. With such a context, we will begin to see patterns such as enter/exit, open/closed, left/right, etc. (I can't find it now, but I saw a documentary once in which the key that allowed us to to translate an ancient text was noticing a pattern where two words were repeated. Someone hypothesized they were "born" and "died" and they were able to crack the rest of it from there. But would she have made that guess if this text hadn't been discovered with a burial ground, as it was?)
Hypothetically, you could contrive a situation where enough context existed to translate a singular isolated text. Numbers are easily translated if enough are present (math being the only known universal language), and if there were corresponding explanations accompanying the numerical notations, this could be enough to crack the code. Getting a bit more out there, if we suspected the text was written by a race we had never encountered but had heard much about, we might come across a translation by trying to make it fit what we know. Or perhaps the material it's written on or the location it was found lead us to believe the text is a specific one we've heard of (e. g. The Holy Book Of Mak'Ra) and we translate it by already having a rough idea what it says.
Any pronunciation will be guess.
We don't even know how Latin was pronounced in ancient times, and we have a lot of information to go on. We are still speaking several languages derived from it. This helps us to guess at the pronunciation, but there is still much uncertainty involved.
In your scenario, we don't have any such clues. Assuming we translate it, the most accurate we could hope to be in pronouncing the language would be knowing which letters are consonants and which are vowels. Any written pronunciation guide will rely on us already knowing how to pronounce the words or symbols used as reference, which we can't possibly know.
Imagine a Japanese speaker learning English solely by learning the translation of each English word he reads. He can now read English fluently but has no knowledge of pronunciation, so he gets a copy of Webster's Dictionary. Even though he understands everything he reads, he won't know how the phonetic spellings are supposed to sound, and will be no closer to knowing English pronunciation. This is the situation we will find ourselves in.