The likely site of the battle of the Hydaspes is somewhere south of Jelum, a city in the Punjab region of modern day Pakistan. While this area is nowadays slightly north of the more forested areas of Pakistan there's no real way to tell what it was like during Alexander's time and non of the sources I have to hand explicitly mention forest.

There are however some other issues with the movies depiction of the battle. It was far from the near disaster for the Macedonian infantry the movie showed. Rather Alexander employed some rather impressive deceit to catch Porus in a pincer movement.

After several days of manoeuvring Alexander stationed Craterus with most of his forces at the ford facing Porus and took 11,000 men half cavalry, half foot upstream to cross during the night. By the time Porus realised he was already outflanked. Even though the Macedonian phalanx took a bit of a mauling from Porus's elephants during the ensuing battle their actual losses amounted only to 320, according to Arrian or 1000, according to Diadorus. Indian losses were far higher amounting to 12,000 dead and 9,000 captured according to Diadorus and Arrian. Porus lost 2 sons and his strongest ally in the region during the battle. So the Hydaspes was not a near loss as depicted in Alexander, rather it was a slightly costly, but still powerful victory!

Also, although Bucephalus apparently died during the battle there's no evidence Alexander received a serious wound.

Finally, as a representative of the Irish people, I'm sorry. I'm so very sorry about Colin Farrell's atrocious accent. It's just not fair you had to go through that.

Sources: Claude Mosse, Alexander, Destiny and Myth. Arian, Anabasis of Alexander Diodorus, Bibliotheca Historica