N1120A
Pattern Altitude
No harm in asking for a certain traffic pattern, especially if it is the normal traffic pattern for the runway you are using.
That said, at your home airport, and airports you frequent, you should probably be familiar with any and all procedures and comfortable flying them, and always be ready for a change. For example, at CMA - where I trained and where I probably use the second most after my current home airport of MYF - people coming over the Conejo Grade from the E/SE will nearly always be told to make a straight in...except when they get really busy and decide to send someone off to the north to make right traffic. Since I know the preferred places to enter the pattern from other flights, I know where to head out and enter the pattern. Similarly, MYF is usually RT for 28R and LT for 28L, but 28R is the only lit runway and thus the only one in use at night. As such, they often have you make LT for 28R when coming in from Mt. Soledad at night, especially with someone who is working the pattern. It helps to be flexible, because Class D airports have a lot more variation in when and how busy they get. It will help your local ATC out a lot if you know and are comfortable with every possible way to get in and out of the airport.
That said, at your home airport, and airports you frequent, you should probably be familiar with any and all procedures and comfortable flying them, and always be ready for a change. For example, at CMA - where I trained and where I probably use the second most after my current home airport of MYF - people coming over the Conejo Grade from the E/SE will nearly always be told to make a straight in...except when they get really busy and decide to send someone off to the north to make right traffic. Since I know the preferred places to enter the pattern from other flights, I know where to head out and enter the pattern. Similarly, MYF is usually RT for 28R and LT for 28L, but 28R is the only lit runway and thus the only one in use at night. As such, they often have you make LT for 28R when coming in from Mt. Soledad at night, especially with someone who is working the pattern. It helps to be flexible, because Class D airports have a lot more variation in when and how busy they get. It will help your local ATC out a lot if you know and are comfortable with every possible way to get in and out of the airport.