What do the yellow speed limit signs on the road near curves or intersections mean?

They are "Advisory" signs. Warning that there is a hazard ahead which requires reduced speed. True, they are not the speed limit, but you can still get a ticket if you exceed that speed; it's called "Disregarding a Traffic Control Device".

I have 22 years experience in putting up such signs. (Speed Limit, No Parking, One Way, etc...).

The yellow speed limit signs on the road near curves or intersections mean you should reduce your speed to whatever is indicated by the sign. Yes, they are actual speed limits and they go into effect at the sign, just as any other speed limit does. After the curve you may return to the original speed limit. Whether you are ticketed for speeding around a curve at higher than the posted speed depends entirely on where the incident takes place. Some highway patrols will just give you a warning, unless there have been a series of accidents at that point and they're tired of picking up bodies. In most cases, if the yellow painted zone is within county or city limits, the county or city police will be happy to ticket you for the offence.

These signs mean you need to slow down a little and use caution because it is a dangerous spot. I don't think you could get a ticket in these areas unless you were over the regular speed limit.

they are the suggested speed...the regular speed limit for that road stays in effect. You will not get a ticket unless you are going over the regular limit.

They are safety guidelines. However, if you took the curve too quickly (ignoring the signs) you could be committing wreckless endangerment.

I think it is a :recommended" speed for that curve.