Around 12,000 Brits are registered in the south Costa Blanca area and their vote could prove decisive in close-run battles in many municipalities including Bigastro.
British consul in Alicante Juliet Maric said: "We would emphasise the importance of the British community using their right to vote."
"If people want to change things, then that is the way to do it."
Former Canadian diplomat Charles Svoboda, who is vice-president of the influential group Abusos Urbanísticos No (AUN), said for many reasons the May 27 elections will be the most important ones since democracy in Spain was established.
He added: "It is also the first time that non-Spanish residents can play a determining role in the results in many areas."
"It is vital that those qualified to do so, exercise their electoral rights after judging what the parties have to offer and their record in delivering on past promises."
"No vote - no change for the better, and expect to be ignored in future."
Rumours that expats may be disenfranchised in their home country by voting at the weekend have been quashed by the British Embassy in Madrid.
A spokesman said: "British citizens maintain their right to vote in national elections for 15 years after leaving the UK." "Local elections in Spain do not affect this right."
So we will see you down at the Ayuntamiento mañana por la mañana.