There is no real way to know your chances of upgrades before you arrive. Some would not agree with me but I certainly find that if you arrive early you have a better chance of being upgraded than if you arrive late. I often arrive very late at hotels (10pm and later) and find that I am rarely upgraded.

However, if a specific upgrade is important to me, I find the individual hotels to be accommodating to my request. I'm sure there are some people that call every single time and try to get every single upgrade possible, but I do not do this.

You should know that getting an upgrade as gold outside of America is even less likely. I would say you have about a 20% chance of an upgrade although I have not stayed at the particular hotel in question. There is a lesser gap in treatment between gold and diamond when staying within the US, but much larger gap when you leave the US. If you have any other questions, feel free to ask. Know that you'll likely be able to find an answer to your question instantly by using the search function. It is much faster than creating a new post or thread and then waiting for someone to reply.