I go to Encinitas, (right next to Cardiff to the north) almost every year. I go in winter so I don't know about the waves in April, but there are a ton of surf spots in the area. The world class ones, like Swami's, are a mob scene full of guys who have been surfing the spot for 20+ years and they all know each other... but there are so many breaks around there you can find stuff.
I don't know the water temps in April but in the middle of winter everyone around there wears a 3/2 (or sometimes a 3/4) full suit, some with booties, some without (I wear booties). I would imagine that April is spring suit weather, doubt many are trunking it except for the big fat dudes with some insulation. Maybe call Encinitas Surf Shop to see if you will need to buy a wetsuit.
I stay at the Moonlight Beach Motel (about $80/night for a two bedroom with kitchen, patio, ocean view of Moonlight beach that is 1 block away). I surf D Street (100 yards south of Moonlight Beach) early in the AM if the tide is not too high. It is a very mediocre beach break but uncrowded if you get out there super early. Walk further south to get the reefs that are just to the north of Swami's and are kind of junky but uncrowded. Walk a mile or so north to Stone Steps, which is a good rock bottom reef with variable crowds. Cardiff is really good too (5 min. drive south from Moonlight Beach motel). I pretty much stay in the Moonlight Beach/Swami's/D Street/Stone Steps neighborhood and don't drive anywhere but if you drive there are probably 50 surf spots within 15-20 minute drive.
If you are going to buy a board I think Hansen's ( giant surf shop in Encinitas) lets you demo ($50/day) and put up to $100 of demo towards a new board. Encinitas Surf Shop is a good hard core small shop that is across the street from the Moonlight Beach Motel, don't know if they have a demo program but they have everything you would ever need for surf gear.
Love that place. If you have a little kid take them to LEGOland when the surf is crappy.