It is necessary if you are like me and not really a fan of cold water, but if you can handle it then no.
FIrst, you should know that the water temperature depends on the swell direction. Waves come in swells. Sometimes we have south swells, when the direction of the waves come from the south. Sometimes, the are West, North, or a combination of the three. Depending on that direction the temperature of the water changes. Of course it also depends on the air temperature, but its important to remember that just because its hot outside, it doesn't mean the water is warm (although you can probably stand much colder water when its hot and sunny).
Sometimes I go out at makaha and it feels like the water is 55 degrees, and other days it feels like 65-70....It's almost deceptive, but I also think its warmer later in the day.
If you want a new suit, you probably have to buy it in a quicksilver, ripcurl, or billabong store in a mall here. Or if you want to support peruvian brands, there is a good one called BOZ, and i hear they have a store in Miraflores. Also there is a surf shop in Miraflores called Klimax, they probably sell suits too.
although if you want a good deal, go to the USA! wetsuits (at least the first three brands i mentioned) seem to be cheaper there.