Press F2 to enter the menu, go to 'setting up the soft dip', press fire. Go to 'slot 1 bomber man', press fire. Confirm that difficulty is set to 4. You can change it with the fire button. Exit the menu by pressing the C button (it's the space bar on the keyboard). In the main menu, go to 'exit' and press fire.
To change the language, hit TAB, go to 'Bios Selection' and change the driver to 'US MVS (2.?)'. Go to 'Reset' and press enter. The game boots and the language should now be set to english.
Make a savegame before the action starts. For some reason, MAME will not remember the driver settings, so when you quit the game and start it again, back to spanish text it is.
Edit: Yep, we play the normal mode.