tl;dr: Within the movie canon, the Uruk-hai are created magically, fully formed, and with the power of Common Speech already part of their minds. Presumably, this includes enough Common Speech to converse with other Uruk-hai, and Orcs, in a casual manner. That Common speech is translated into English on our behalf, and likely included idioms that were not translated directly.
First of all, it's important to note that the movies dramatically differ from the novels in this regard.
In The Books
In the novels, the Uruk-hai aren't speaking English, or even Common. When speaking to each other, or their superiors like Sauron, the Uruk-hai speak their own dialect of the Black Speech. Though Sauron intended for the Orcs to also use the Black Speech, they mostly did not; by the time of the novels/movies, they had settled on a corrupted form of Common that was used by the various Orc tribes, and which the Uruk-hai would have used to order them around. So, had the scene from the movie occurred as filmed in the novel, it's not clear what language the Uruk-hai would have used (he was speaking to his fellow Uruk-hai, but he was speaking at the Orcs.)
In order for us to understand anything written in the novels, it must be translated (possibly twice, as Bilbo/Frodo/Sam might have translated any Black Speech into Common Speech when for the benefit of readers of the Red Book itself.) So, if an Uruk-Hai were to say something idiomatic, like "back on the menu", that is merely a (Black Speech ->) Common Speech -> English translation of whatever the Uruk-hai was really saying, likely an idiom that meant the same thing to the Orcs. (Note that this is a hypothetical example: no Uruk-hai says anything like that in the books.)
Secondly, the way the movie portrays the creation of the Uruk-hai by Saruman is vastly different from the novels. In the original source, they are born and bred (by cross-breeding orcs and humans, IIRC). They grow and are trained and taught just like any other member of the Black Armies.
In The Movies
In the movies, the language issue is much clearer: everyone speaks Common all the time. We know this because other characters (like Merry/Pippin/Sam/Frodo) all understand their speech, when I seriously doubt any of them can speak Black Speech.
However, even in Common, the phrase "back on the menu" is a highly anachronistic idiom: the word "menu" in it's current sense didn't even enter the English language until the 1800s. Again, we have to assume that the Uruk-hai said something in idiomatic Common that was translated into idiomatic English as "back on the menu", and almost certainly did not translate literally.
Jackson also chose to shortcut the process is of their birth by showing Saruman essentially "growing" them somehow. And we can see the Uruk-hai emerging, fully-formed, and already able to understand Saruman's speech (also presumably Black Speech.)
So, whatever process Saruman uses to grow the Uruk-hai fully formed, it must also include imbuing them with the power to speak and understand language, or he wouldn't be able to give them orders or hear their status reports.
Age and Life Span
Neither the novels nor the movies give us any good indication of how long an Uruk-hai can be expected to live, nor how long they are "raised" before going into battle.
Obviously, in the movies, the age when they are considered battle-ready is a non-issue, as they are created fully-formed and battle ready immediately. However, in the books, they are bred naturally, so there must be some growing period before they are ready for fighting. Given their nature as, essentially, bred soldiers, I expect the age is rather young, probably as soon as they get past whatever passes for puberty and are physically capable of fighting.
Their lifespan is also never really discussed in the novels, but there is speculation that they are immortal, or at least very long-lived. Remember, Orcs are basically corrupted elves, and Uruk-hai are Orcs bred with humans, so there is a good chance they would have lifespans on the scale of elves and the Dúnedain.
The one concrete example we have to support this idea is Bolg, the Orc chieftain at the Battle of the Five Armies. He is the son of Azog, who (in the novels) was killed by Dain in 2799. At that point, Bolg was already old enough to take his father's place as chieftain, and he still held that position in 2941, almost 150 years later, with no signs of growing old or infirm.
Whether an Uruk would have a longer or shorter life span is never really discussed. On the one hand, with their human genetics mixed in, you'd expect a shorter one. On the other hand, they are supposed to be better, strong, faster Orcs, so you'd expect a longer one. Unfortunately, as far as I can find, there are no references in any of Tolkien's writing, including the Lost Tales and other supplemental stuff, that gives a good answer.