I live in San Francisco and drive a stick shift. The stick is good as an option to killing the breaks when going down a steep hill, but I worry about the noise caused by high RPMs. How many RPMs can the engine take?
High rpms? down hill? just how are you driving this thing?,
the rule for using a stick shift on hills is, use the same gear going down that you used going up. Unless you are driving like “bullet” in that old movie, you should not be revving the engine on the down hill. Anyway, adjust the engine speed before you downshift, dont let the clutch do that for you or you will wear the clutch excessively.
I meant brakes, of course.
The red line on the tachometer is the maximum RPM for which the engine is designed.
Don’t exceed the red line, and don’t be afraid to use the brakes.
Brakes are cheap. Engines are expensive.
I would say I am using the same gear going down the hill as I am going up. RPMs are 4000 at most going downhill, well short of the red line on the tachometer. And I don’t downshift once I start my decline. I guess I am just concerned about the loudness of the engine at that many RPMs.
High rpms? down hill? just how are you driving this thing?
1st gear, clutch out completely, and watch the tach creep toward the redline as the car rolls downhill. Apply brake as necessary to keep engine out of redline. San Francisco is one of the few places where a car gains speed while engine braking in 1st gear.
Due to improved engine power, truckers now go downhill in a lower gear than they would use to go up a hill. I often let my engine rev to around 5k when going downhill. 130k miles and still going strong.
Although I don’t do this often, it is ok to grab a lower gear while heading downhill. Sometimes it is necessary when you’re following someone going slower than expected. Heel and toe is not just a racing technique.
Are you still practicing how to drive? Just be careful… 
4,000 rpm coasting downhill is not excessive in a Miata. The engine seems to enjoy 4,000 to 5,500 rpms.
Enough with this “how do I drive down a hill” How many times just in the past 6 months have we seen this type of question? Along with the “oil change interval”, “timing belt interval” and many many others that are all covered in THE owners manual. If you don’t have one GET one.